This is marked on the OS map as ‘Long Cairn’.
The ‘cairn’ part I might argue with, but ‘long’, well there’s no disputing that one. It is hard to judge the size of the mound as it extends and tails off into the trees, the eastern end looks a little too truncated and its base appears to have been cut into.
If you’re visiting the nearby falconry centre, give it a look and see what you think.