The story of Egbert’s Stone is an early English rather than a megalithic one, of course: in 878ce, King Alfred rallied armies from three counties (Somerset, Wiltshire and Hampshire – apparently the Dorset men were occupied at the coast) to fight the Danes.
Tradition has it that they met at Egbert’s Stone – and there are at least three different sites claiming to be that of the stone (others being a three-counties boundary post at Bourton, and the site of the 18th century folly King Alfred’s Tower – both are a few miles from Kingston), although it seems that the Kingston Deverill site (or, rather, Court Hill, where the stones are assumed to have come from) is regarded as the strongest claimant.
After the armies met, they marched to Ethandun (Edington) and defeated the Danes – somewhere near the White Horse of Westbury/Bratton.