From A Handbook For Residents And Travellers in Wilts And Dorset, published by John Murray, 1899:
Yarnbury Camp, a very perfect and interesting work, placed on the summit of a solitary eminence of the great Plain, the undulating surface of which is seen from it in a panoramic view. It is circular, and of great size, the entrenchments being two banks and ditches, the inner about 50ft. deep. The principal entrance faces the E., and is defended by a complicated outwork. Another entrance on the S., should be noticed for its complete preservation. E. of Yarnbury are Steeple Langford Downs, with singular and diversified earthworks and mounds, probably the sites of huts. On the 4th of October Yarnbury is the scene of an annual fair for the sale of sheep and colts. The old road from Salisbury to Bath (now but little used) skirted the camp on the E., and its course is still marked by many of the milestones.