Prehistoric Engravings Discovered on Stonehenge's Altar Stone

In the Historic England archive of Richard Atkinson's 1958 excavations at Stonehenge, I came across two photographs (link to full size copies)  that revealed an astonishing and unexpected feature of the Altar Stone. The photographs, labeled P50106 and P50107, partially show the excavated southeastern end of the Altar Stone, which has otherwise always been buried. (There is a possibility that they are on the south side of the stone instead) To my surprise, there appeared to be prehistoric engravings on it.

In his 1979 book on Stonehenge, Atkinson merely noted that the stone was deliberately worked. However, with the benefit of recent knowledge about prehistoric engravings on stones and ceramics from across the British Isles, the diagonal lines on the altar stone can now be clearly identified as part of that tradition. These lines are more than just functional stoneworking or accidental damage, they have a meaning.

This preliminary identification of the alternating diagonal lines, which indicate they were inscribed by stone tools, is just the beginning of a larger debate. Questions arise about their connection to the builders of Stonehenge, their meaning, and their origin. Given this significant discovery, it is crucial to reopen the previous excavation for a modern, detailed examination. This would ensure that any speculation is grounded in realism.

My sketch of the engravings:

The photos are on https://www.sarsen.org/2024/10/examining-physical-properties-of-altar.html and at https://historicengland.org.uk/images-books/photos/item/P50106 and https://historicengland.org.uk/images-books/photos/item/P50107 

I paid for them to be digitised and they are now available online, the embeded versions are below.

To confirm that this is the eastern end of the Altar Stone I compared different photos and matched up features. It isn't certain, the south side is also a possibility - https://www.sarsen.org/2024/10/are-engravings-actually-on-altar-stone.html