The post-Roman road wandered off for two and half miles () through Colsterworth, but Ermine Street continues as the B6403, through Ancaster to the A17. It then continues as a public right of way, easily walked, until Waddington airfield blocks it at . The route from Colsterworth, through Ancaster, to Bracebridge Heath is known as High Dike. It runs roughly parallel with and to the east of the A607 between Carlton Scroop and Harmston. High Dike takes to the level, open, dry country of the Lincolnshire Heath while the A607 wanders through the villages on the spring line below. From the Antonine Itinerary there is known to have been a Roman Settlement on the road in South Lincolnshire, called "Causennae" which has been variously identified with Ancaster Roman Town or Saltersford, south of Grantham.