“It is believed that the entire summit of Warton Crag was once a fort, built by the Brigantes (an early British tribe) in the 1st century AD, making use of the defences provided by the natural rock formation. The path crosses the remains of semi-circular ramparts which can just be traced within the woodland to the north of the summit. The fort evidently gave Warton its name, meaning the turn (town) by the Weard (a watch place, or look-out)”
From
(which also gives very detailed directions for the walker)