Thursday 31 May 2018

The Stonehenge Glacier Theory- Time To Let It Go....

The snow glows white on the mountain tonight
Not a footprint to be seen
A kingdom of isolation
And it looks like I'm the queen

The wind is howling like this swirling storm inside
Couldn't keep it in, heaven knows I've tried
Don't let them in, don't let them see
Be the good girl you always have to be
Conceal, don't feel, don't let them know
Well, now they know

Let it go, let it go
Can't hold it back anymore
Let it go, let it go
Turn away and slam the door
I don't care what they're going to say
Let the storm rage on
The cold never bothered me anyway

Let it go, let it go..

(c) Kristen Anderson-Lopez Robert Lopez

Video available:

Wednesday 30 May 2018

UNESCO response to the UK A303 Stonehenge Statement

Analysis and Conclusion by World Heritage Centre and the Advisory Bodies in 2018

UK 2018 Stonehenge State of Conservation Report


1.   Executive Summary of the report

In accordance with Decision 41 COM 7B.56, the United Kingdom State Party has produced a State of Conservation Report (SOCR) for the Stonehenge, Avebury and Associated Sites World Heritage Site.

This SOCR updates the Committee on changes made to the evolving A303 trunk road proposals in response to the 2017 WH Committee decision and the technical advice of the June 2017 Advisory Mission report. This updates the report which was submitted to the World Heritage Centre on March 30 2017.

Specifically, in response to the Committee’s decision, this report provides updated information on the proposed A303 improvement within the WH property, including changes made to protect and transmit the OUV of the property through the scheme design and associated mechanisms. It provides information on road scheme options to which the Committee recommended further consideration should be given and reports on progress made in implementing the recommendations of the 2015 and 2017 Advisory missions.

The report is structured according to the format provided by the World Heritage Centre. The clauses of the World Heritage Committee decisions are given in italics and indented. The response of the State Party is not indented and does not use italics.

2.   Response from the State Party to the World Heritage Committee’s Decision,
paragraph by paragraph.

The World Heritage Committee,
1.   Having examined Document WHC/17/41.COM/7B.Add,

2.   Recalling Decision 35 COM.7B.116, adopted at its 35th session (UNESCO, 2011),

3.   Takes note with satisfaction of the management achievements, and progress with implementation of previous Committee Decisions, to address protection and management issues identified in the Statement of Outstanding Universal Value (OUV) for the property.

4.   Commends the State Party for having invited two Advisory missions to advise on the process for determining and evaluating options for the proposed upgrading of the main A303 road across the property, as part of a wide major infrastructure project;

Since the 2017 meeting of the World Heritage Committee, a third Advisory mission was invited by the State Party and took place from 5th  to 7th  March 2018. The purpose of the Advisory mission was to enable the State Party to receive the views of the World Heritage Centre and ICOMOS on the scheme for the proposed A303 road improvement which is the subject of public consultation at the time of writing.

5.   Expresses concern that the 2.9km Stonehenge tunnel options and their associated
2.2km of dual carriageway approach roads within the property that are under consideration, would impact adversely the OUV of the property;

In response to World Heritage Committee Decision 41 COM 7B.56, the feedback from UK heritage bodies and from the wider UK heritage sector and from civil society, concerning the potential negative impact upon the OUV of the WH property of the 2.9km tunnel options consulted upon in January-February 2017, Highways England significantly modified the proposed scheme.

The new scheme proposal has been pulled back from the SW quadrant of the property to take a new alignment close to the south side of the present A303 surface road. This resolves the previous scheme impacts on the winter sunset solstitial alignment as viewed from Stonehenge – the revised scheme infrastructure has no interaction with this key
astronomical alignment, with the proposed western tunnel portal and new surface approach road situated well to the north-west of the previous scheme. By pulling the route alignment
back to closely follow the current surface A303, the new road avoids impacting adversely upon the setting of the two new long barrows identified during archaeological field evaluation
in 2016.

The new alignment also means that the length of new road within the western part of the property is reduced to c.1km. The route now proposed also has a significantly reduced impact upon the setting of the property by avoiding:
      the need for a large cutting through the crest of Oatlands Hill, which forms the backdrop to the property in its SW quadrant (i.e. to the south and west of the current
surface A303), or
      a new junction just outside the SW corner of the property at The Park, where geophysical survey has identified a previously-unknown Bronze Age round barrow cemetery.

The revised scheme proposal removes an adverse impact on the setting of the Normanton Down barrow cemetery by positioning the western portal in a less obtrusive location to the north-west of the barrow group.

The length of bored tunnel would be c. 3 km and has been extended westwards by a further c. 200 metres of cut-and-cover tunnel which serves two purposes:
      it positions the point where traffic emerges from underground to a location near the head of a shallow dry valley, which minimises the visual intrusion as viewed from Normanton Down; and
      it allows the post-construction reinstatement of the land-form above the cut-and- cover section to match the existing ground surface thus helping to protect the setting
of the Normanton Down barrow group.

The new route from the western tunnel portal to the western edge of the property has been designed to be in a c. 8m deep cutting, with vertical sides and rounded grassed shoulders. This option would minimise the land-take for the new road within the WHS, while the depth of cutting will remove the visual intrusion of the moving traffic, particularly heavy goods vehicles, from the sightlines between many of the groups of sites and monuments that convey the OUV of the property.

At the western boundary of the property, where the current surface A303 has a junction (Longbarrow Roundabout) with the current surface A360 road, the new scheme proposal will completely remove the present, highly intrusive roundabout. A replacement junction will be positioned some 600m beyond the western boundary of the World Heritage property. This will also remove c.600m of the A360 to both the north and south of the present Longbarrow Roundabout (a total of c.1.2km) and reposition it away from the property to connect with the new junction. This will have a positive impact upon the OUV of the property, with a substantial improvement on the setting of the Winterbourne Stoke barrow group and the

recently identified Diamond group of sites and monuments that convey the OUV of the property.

The new junction 600m beyond the western boundary of the World Heritage property and the new A303 road within the property will all be free of lighting (although the interior of the tunnel itself will need to be lit), thus having a positive impact upon dark skies and the appreciation of astronomy compared with the current surface road and Longbarrow Roundabout.

The site of the current Longbarrow Roundabout and the redundant sections of the current A303 both within and without the property, plus the redundant sections of the A360 north and south of Longbarrow Roundabout, will be removed of all current infrastructure and returned to traditional Wiltshire chalk-land byways for walkers, cyclists, and horse riders.

At the eastern end of the bored tunnel within the World Heritage property, a second extension to the tunnel of c.100 metres has been designed to achieve a location for the eastern portal with the minimum level of visual intrusion which optimises the beneficial
effects of removing the current surface road within this part of the WHS. The revised location offers a greater degree of landscape mitigation for the eastern portal, which will only be
visible from close-up viewpoints.

Whilst some impacts may occur on the setting of heritage assets beyond the scope of WHS inscription, such as an Iron Age hillfort and an 18th  century Registered Park and Garden which lie farther to the east of the eastern portal location, the proposed location of the eastern portal will avoid any negative setting/visual impacts to sites and monuments that convey the OUV of the property. The relocation of the portal some 100 metres east of the
2017 location further protects the Stonehenge Avenue, which is now located c.150 metres west of the portal site (and whose previous location in the 2017 consultation was based on the recommendation of the 2015 Advisory mission).

It will also completely remove the intrusive impact of the current surface road and its heavy traffic when viewed from Woodhenge and Durrington Walls henge. From the eastern portal to the eastern boundary of the World Heritage property, the new scheme proposal lies almost entirely within the existing highway boundary and will largely re-use the existing highway infrastructure.

6.   Urges the State Party to explore further options with a view to avoiding impacts on the
OUV of the property, including:

1.   The F10 non-tunnel by-pass option to the south of the property,

2.   Longer tunnel options to remove dual carriageway cuttings from the property and further detailed investigations regarding tunnel alignment and both east and west portal locations;

Following Committee Decision 41 COM 7B.56 the State Party gave further consideration to both F10 and longer tunnel options before the preferred route was announced. This consideration was based on the evidence provided by Highways England as part of the development of the route options which were discussed during the 2017 Advisory mission. The State Party concluded that neither F10 nor the longer tunnel options were viable but acknowledges that although the evidence that had been submitted to the 2017 Advisory mission was extensive, the reasons why these particular routes were not deliverable had not been clearly articulated. Further work has been undertaken by Highways England to better collate the evidence and set out more clearly the reasons why neither the F10 southern

bypass nor the longer tunnel option are deliverable. This information was presented by
Highways England to the 2018 Advisory mission and is summarised below.

F10 non-tunnel bypass.

In cultural heritage terms, although the bypass around the southern edge of the property could result in a lower impact upon the property from new infrastructure development, there would still be impacts upon the setting of the property given the proximity of the F10 route alignment to the south of it. The landscape to the south of the WHS property is itself a very rich archaeological landscape which contains a high potential, as revealed by archaeological investigations not associated with the proposed road improvement, to contain extensive sites and monuments relevant to the period of OUV for which the property is inscribed. In
response to a question about the F10 route from a member of the March 2018 World
Heritage Centre/ICOMOS Advisory Mission, Professor Sir Barry Cunliffe, said that, given the high archaeological potential of the land to the south of the property route F10 would likely impact more heavily on significant archaeology of the Neolithic and Bronze Age periods, compared to the known, low potential for significant archaeology relevant to the period of OUV within the footprint of the currently proposed scheme within the WH property.  He also referred to the boundary having been established over thirty years ago and that it would be the subject of review.

There is a further critical disadvantage of F10 for the WH property as a result of its poor performance in dealing with traffic flows. Because the F10 route would involve a total diversion from the current A303 of 22km and because its principal junctions would be located significant distances away from their current locations, it would not resolve the chronic traffic issues which blight the local road network within and beyond the Stonehenge
component of the WH property. In these circumstances it is almost inevitable that the current surface A303 through the WHS would need to remain open to traffic to provide the required connectivity between local communities and to alleviate pressure on the local roads around the boundaries of the property.

The retention of the current surface A303 would negate the strategic benefit for the property that would be delivered by the proposed scheme, of removing much of the existing, intrusive surface road so that the two halves of the property to the north and south of the current road, can be reunited over a distance of c. 3.3km and the full potential of the WHS realised in
terms of both its condition and the public appreciation of its full range of sites and monuments.

In natural environment terms, route F10 would have an impact upon the Rivers Avon and Till Special Area of Conservation (SAC). The SAC is protected by the European Union Nature Directive and benefits from the highest level of statutory protection. The State Party understands that an EU level designation does not equate to the same level of significance as a WHS but nevertheless the UK government is under a statutory duty to protect sites subject to an EU wide Directive. Route F10 would involve two substantial viaducts and embankments crossing the two river valleys where they are deeply incised and where the special qualities of the SAC inscription are most strongly expressed.

Given its protection by EU Directive, its poor fit with the local road network, and the overall extent of adverse environmental impact that would be caused by 22 km of new dual carriageway through currently undisturbed high value countryside, route F10 is not a viable option. It is not an option that can be supported by the State Party

Longer tunnel options – Highways England’s work to look at longer tunnel options has shown why a longer tunnel option scheme is not deliverable.

At the western end of the WH property, the rising ground to the west of the property, known as Oatlands Hill, dictates that a tunnel continuing beyond the property boundary would need to traverse the width of the hill before it could emerge where the ground begins to descend into the Till valley, east of Winterbourne Stoke. This would extend the tunnel westwards at least 1.8 km, at an additional cost of c. £540m. The extension would be impractical in terms of accommodating a safe new junction connection with the A360 which would have to
remain on its existing alignment at the western boundary of the WHS property. As well as reducing the benefit for the Winterbourne Stoke Barrow Group by the retention of the A360 in its current alignment, the location of the new junction so far west of its optimum location would mean that local communities would still suffer from rat-running traffic. The substantial additional cost entailed in this would make it unlikely ever to be achieved, particularly when assessed in relation to what the State Party sees as the limited additional heritage benefits that would be delivered by this option above those offered by the current scheme.

At the eastern end of the proposed scheme the presence of the River Avon makes it impossible to create a tunnel portal just beyond the WH boundary without the construction having an unacceptable impact on the Rivers Avon’s international status as a Special Area of Conservation (SAC). To the east of the Avon, the proximity of the Solstice Park junction and the rising ground means that the tunnel would have to be extended at least 4 km eastwards, at an additional cost of c. £1.2 billion, before it could emerge at a suitable
location. The extension would remove the existing A303 junctions with the A345 at Countess
Roundabout and at Solstice Park, wholly disrupting the operation of the road network both locally and more widely, with consequent adverse impacts on nearby communities. As with the western extension, while the eastern extension of the tunnel could secure some degree of heritage benefit, the stated disadvantages and additional cost mean that this would be an extremely poor value for money option. It is not an option that could be supported by the State Party.

A longer tunnel with the eastern portal further east than that shown in the proposed scheme but still within the WH property would cause greater impacts on nationally-important designated sites such as Vespasian’s Camp Iron Age Hillfort and the Grade II* Registered Park & Garden (RPaG) at Amesbury Abbey. In addition it would impact negatively on the nationally-important Mesolithic site recently discovered at Blick Mead, just east of Vespasian’s Camp and within the RPaG. Most significantly, but not related to heritage, a tunnel portal further east within the WH property would harmfully impact the groundwater flow to the River Avon SAC and would not secure planning consent.

7.   Encourages the State Party to address the findings and implement the recommendations of both Advisory missions and to invite further World Heritage Centre/ICOMOS Advisory missions to the property, to be financed by the State Party, in order to continue to facilitate progress towards an optimal solution for the widening of the A303 to ensure no adverse impact on the OUV of the property;

Substantial, positive progress has been made in implementing the recommendations of both mission reports. Notable achievements, beyond those mission recommendations covered elsewhere within this SOCR include:

      The establishment of the independent Scientific Committee of eminent archaeologists who are subject-matter experts in the heritage of the WHS. Chaired
by Professor Sir Barry Cunliffe, the Committee plays an active part in advising on the
scope and standards of archaeological assessment, evaluation and (ultimately)
mitigation to be applied to the proposed scheme. The Committee also considers and

provides advice on matters relating to the OUV of the property. The Committee also includes representatives of the Heritage Management and Advisory Group (HMAG) who are members on behalf of their respective organisations: Historic England; English Heritage Trust; National Trust and Wiltshire Council.

      The implementation of studies into future visitor behaviour after the removal of the existing A303, including sustainable tourism management and ‘masterplanning’ for the future interpretation of the WHS and transmission of its OUV have been commissioned and a landscape-wide strategy is currently being developed.

      A legacy for the WH property, based on the vision enshrined in the 2015 WHS Management Plan is being developed in partnership with the WHS Coordination Unit and stakeholders.  This is designed to produce proposals to achieve significant benefits for the WH property which will be considered for inclusion with the future scheme consent application.

      A wider consultative engagement with stakeholders and civil society has been achieved through the establishment of a Local Community Forum and by establishing scheme links and liaison with stakeholder groups such as the Avebury and Stonehenge Archaeological and Historical Research Group (ASAHRG). In addition direct stakeholder contact has been set-up as an integral part of Advisory mission business, with a substantive face-to-face session taking place as part of the latest, March 2018 Advisory mission.

The State Party is committed to maintaining substantive dialogue with the WH Centre and its advisory bodies through an ongoing and iterative series of advisory missions at appropriate junctures in the development of scheme proposals. The latest, third, Advisory mission has just concluded, having run from the 5th  to 7th  March 2018. Consideration will be given to further advisory missions as appropriate.

8.   Requests the State Party to manage the timing of the consent and other statutory processes for the A303 trunk road project to ensure that the World Heritage Centre, ICOMOS and the World Heritage Committee can continue to contribute to the evaluation and decision-making processes at appropriate stages;

The State Party has secured the adjustment of the consent and other statutory processes for the A303 trunk road so that the advice of the March 2018 Advisory mission and the decision of the 2018 WH Committee will be received and thoroughly considered before the A303 proposals are submitted as a Development Consent Order (DCO) application, likely to be in the Autumn of 2018. Likewise, any further decision by the WH Committee at its 2019 session will also be thoroughly considered by the State Party ahead of any decision on whether to grant the scheme it’s Development Consent Order.

3. Other current conservation issues identified by the State(s) Party(ies) which may have an impact on the property’s Outstanding Universal Value

There has been progress in several areas that will benefit the World Heritage property over the twelve-month period since the Committee last considered the state of conservation of the property in 2017. There remain ongoing challenges in areas that have been identified in the Protection and Management Requirements section of the Statement of OUV and in the most recent completed cycle of Periodic Reporting for Europe in 2013. Positive developments are summarised below as well as the ongoing challenges including the proposals for the improvement of the A303.

Progress towards establishing an independent and sustainable Stonehenge and
Avebury World Heritage Site Trust

The World Heritage Site Management Plan Policy 8b underlines the need to seek adequate funding for the coordination of the WHS and the implementation of the Management Plan. The World Heritage property partners are in the process of establishing an independent trust.  The trust is designed to ensure that the arrangements for the overall management of the World Heritage property and the delivery of the Management Plan are both adequately resourced and sustainable.  This is particularly important in a time of reduced public sector funding in the United Kingdom where diversifying income is a key to sustainability. The current World Heritage Site Coordination Unit relies solely on public funding from Wiltshire Council and Historic England.

World Heritage property partners, with assistance from a Heritage Lottery Fund Resilient Heritage grant, are supporting an evidence-based strategic development programme which will include the transition of the planning, coordination, monitoring and advice function to an independent trust. Strengthened governance and revitalised relationships with partners and stakeholders will underpin a trajectory towards sustainable growth.  The establishment of an independent trust will greatly enhance the potential to raise funds and thereby add substantial value to the World Heritage property, its partners and the wider community. The additional funding will enable the World Heritage Site Trust to progress significantly with the implementation of the Management Plan and deliver the ambitious landscape scale strategies envisaged in it. Related interpretation projects will encourage greater understanding of the significance of the whole World Heritage property and deeper engagement with its protection and management.

World Heritage Property Setting Study and Boundary Review

There is a specific and robust policy in the Local Development Framework to protect the Outstanding Universal Value of the property from inappropriate development, along with full references in relevant strategies and plans at all levels. The Wiltshire Core Strategy, formally adopted on 20th January 2015, includes a specific World Heritage Property policy.  Policy 59 requires that precedence should be given to the protection of the WHS and its OUV. This policy also advises that additional planning guidance be produced to ensure its effective implementation.  Work on the setting study proposed as part of this guidance has reached
the detailed draft brief stage. This has been developed with the input of a range of heritage and landscape expert partners. The work will be commissioned in the coming year. The
study is designed to provide guidance on the identification of the setting and the type of development that is likely to have an impact on it and the World Heritage and its OUV.   It
will also provide advice on the nature of evidence likely to be required from developers.

The study will be informed by the Statement of OUV and identified attributes as well as Historic England’s Guidance on the Setting of Heritage Assets Historic Environment Good Practice Advice in Planning Note 3 (Second Addition) 2017.  This sets out guidance against the background of the National Planning Policy Framework and related guidance in the Planning Practice Guide on managing change within the setting of heritage assets.  The ICOMOS Guidance on Heritage Impact Assessments for Cultural World Heritage Properties (2011) will also inform the study. These existing documents today form a robust basis for the assessment of impact on the World Heritage property through change in its setting and inform the approach to assessing impact in current development proposals.

The boundary review at Stonehenge will be progressed following completion of the setting study.

Conservation: Cultivation and Burrowing Animals

The first joint Stonehenge and Avebury WHS Condition Survey was produced in 2012.  The summary of this joint Condition Survey noted a positive change to the overall condition of monuments. This analysis was confirmed by the broad stability of monuments in good and fair condition. These encouraging findings result from a great deal of positive management
of the attributes of OUV by the partners engaged in both parts of the World Heritage property including national organisations and local landowners and farmers.

The results of the Condition Survey show that the two most significant threats to the physical remains that contribute to the OUV continue to be cultivation and burrowing animals. There has been a significant increase in the presence of the latter over the decade since the preceding condition surveys. Work to protect vulnerable monuments from damage by cultivation and from badgers and other burrowing animals are therefore two of the key priorities of the World Heritage Management Plan (2015).

Agri-environment schemes remain the most effective response to protecting sensitive archaeology from damage through cultivation.   These schemes are extremely important for protecting the physical remains and enhancing the setting of prehistoric monuments through measures such as grassland restoration and scrub control. At Stonehenge around 40% of the WHS landscape is in environmental stewardship helping to protect and/or enhance the setting of c. 500 historic features.  At Avebury too around 40% of the WHS is in these schemes which benefit c. 300 historic features.

Work on designing a brief for the World Heritage Property Burrowing Animal Strategy will continue this year. Funding will be sought to undertake the necessary baseline studies and, following a review of existing research, the design of an innovative landscape scale strategy for managing this impact.

Roads and Traffic

Despite the very substantial progress delivered by the closure of the A344 the impact of roads and traffic remains a major challenge in both parts of the World Heritage property. The dominance of roads, traffic and related clutter continues to have a harmful impact on
integrity, the condition and setting of monuments and the ease and confidence with which visitors and the local community are able to explore the wider property.   At Stonehenge the A303 remains a problem.  The current Highways England scheme and its ability to address these issues is discussed above in relation to the WH Committee 2017 decision.

At Avebury, a strategy has been developed to identify a set of actions to address road and traffic related challenges, which include the impact of A4 on the setting of Silbury Hill and other attributes of OUV, and the erosion to some areas of the West Kennet Avenue where a minor road passes over and alongside the monument. This Avebury WHS Transport
Strategy (2015) Strategy-2015.pdf takes a holistic approach to road and traffic issues within the WHS.  It has
established an approach and recommended schemes agreed by delivery partners, curators,
managers and representatives of the local community to balance the concerns of all parties and safeguard the WHS while retaining a viable transport network. It includes a set of design
principles and specific outline schemes.

Work has been undertaken during the last twelve months in partnership with the local community to produce initial feasibility studies for some of the schemes proposed in the Strategy.  This includes work related to the narrowing of the A4 to reduce its dominance in the landscape by calming traffic and encouraging exploration of the WHS.  This will be even more important if visitor numbers see an increase during development of the A303 improvement scheme or in response to The Great West Way initiative to develop a tourist route along the A4 from London to Bristol.  In addition, Wiltshire Council has indicated that they are willing to progress with work to further the move to a Traffic Regulation Order on the

Ridgeway National Trail; a Byway Open to All Traffic (BOAT) in the Avebury half of the
World Heritage property where motorised traffic is currently causing damage to archaeology.

4. In conformity with Paragraph 172 of the Operational Guidelines, describe any potential major restorations, alterations and/or new construction(s) intended within the property, the buffer zone(s) and/or corridors or other areas, where such developments may affect the Outstanding Universal Value of the property, including authenticity and integrity.

Army Rebasing 2020

The Ministry of Defence has progressed with the planned development north of Stonehenge at Larkhill Garrison, which is part of the Rebasing 2020 project.  The final location and design of this scheme has demonstrated sensitivity to the protection of the WHS and its setting.  It is important that any additional or consequential development continues to take into account the need to protect the World Heritage property and its OUV.

Future Boscombe Down Development: Boeing Defence UK New Aircraft Hub

This development in the setting of the Stonehenge part of the World Heritage property is at the master planning stage.  This is a major project that aims to redevelop the existing military airfield to the southeast of the World Heritage property near Amesbury to include a Boeing
‘centre of excellence’ for its UK business.  A possible 1500 new jobs have been discussed.

The developers have been asked to produce an HIA following ICOMOS guidance.  It is essential that any proposal brought forward identifies and adequately mitigates any harmful impacts on the World Heritage property and its OUV.

It will be important to assess cumulative and consequential impacts of development in the setting of Stonehenge from this proposed major development, the Army Rebasing project and the A303 scheme as well as planned expansion of housing.  High level strategic
engagement is required to ensure infrastructure planning is coordinated to minimise intrusion in the setting of the World Heritage property and avoid harm to OUV.

5. Public access to the state of conservation report

Note: this report will be uploaded for public access on the World Heritage Centre’s State of
conservation Information System (

The State Party agrees that the full state of conservation report should be made publicly
available via the WH Centre’s Information System

6. Signature of the Authority

Wednesday 16 May 2018

Moving a megalith in France

Archeologist Jean-Baptiste Piketty (1827–94) wanted to be buried in a dolmen, so – despite some opposition – in 1896 bought the Ker-Han dolmen in the commune of Saint Philibert (Morbihan), Brittany, and arranged for it to be transported to the Cimetière des Longs Réages in Meudon-sur-Seine, Hauts-de-Seine, France (*)

Click to enlarge - picture from Glyn Daniel Megalith in History

The Science of Prehistoric Stone Transport

Déplacement des mégalithes extraordinaires sur le littoral morbihanais, modèles d'embarcations et questions relatives à la navigation atlantique dès le V ème millénaire AVJC

Trans: Moving extraordinary megaliths on the Morbihan coastline (South Brittany), boat models and issues relating to Atlantic shipping from the 5th millennium BC

An interesting and detailed paper to download: The paper is in French, which you being a well educated sophisticate will not find a problem but I did, but the gist is clear enough.

Incidentally I am happy that the Bluestones could have been brought to Stonehenge overland on the "A40 route", but that might just be my prejudice against getting into boats.