Historic England date this impressive tin mining earthwork as early as "Medieval with later opencast lode tin working." It is an impressive gully, running in a north-east to south-west direction for about 100 metres, on the north slopes of Skir Hill. Later maps name the extensive works along the Wo Brook (O Brook on OS Maps) as 'Henroost Tin Mine', but 'Hexworthy' and 'Hooten Wheals' are also recorded.
William Crossing, in 'One Hundred Years on Dartmoor', published 1901, tells us that; "About twelve years ago a mine was opened near Hexworthy, on the site of some old workings, and for a time yielded tin of excellent quality. But it shared the fate of too many of the Dartmoor ventures, and after some years was closed."
The gully has been estimated as being 10 metres wide and 10 metres deep in places, with wonderful exposed granite walls and outcrops, none of which would have seen the light of day without the extraction of the tin ore. This would have been a huge blot on the landscape in its heyday, but now nature has reclaimed the scar and it makes for a pleasant stroll from Hexworthy.