The word "ancient" covers a vast period. If--as I have proved--the tumps or burys are sighting tumps, excavations also prove that they usually date back to the Neolithic age, which, according to Mr. Ault's recent "Early Life in Britain," cannot be later than 2,000 B.C., and may be 4,000 B.C. A prehistoric trackway might, therefore, be planned and made more than three thousand years before the Old Road (which is a route rather than a road) was devised or evolved--as Mr. Belloc so well describes--as a Pilgrim's Way from Winchester to Canterbury.
I have found that the persistent things down the ages are not the courses of the roads or tracks, but their sighting points, and that cross roads with a place name are such. Place names are also persistent, some of them going back to prehistoric times, but others evidently mediæval. But the real dating of the leys and when the system fell into decay is for future investigation.