The one thing we know about the North Barrow at Stonehenge is that it isn't a "barrow". This circular feature with a an outer bank, ditch and flat central section held a missing Station Stone originally. Where it fits into the chronology of Stonehenge is unclear. Atkinson's section of it is badly recorded and fails to answer one of the fundamental questions, is the circular structure older or younger, is it overlain or does it overlie the main henge bank. Even the age of it in relation to the Aubrey holes in it is unclear.
The best evidence seems to be from Sharpe's balloon photo which to my mind shows the barrow as a complete circle (partly destroyed by the track, with the henge bank overlying it, but others see the photograph as proving the opposite.
I also attach a detail from a photo Adam Stanford took this summer which shows the parch marks and a hint of the position of the Station Stone on the very edge of the path.
Click to embiggen