At the end of the wood, we leave Colsterworth parish. Three kilometres from the start, at the hamlet of Birkholme, the road finds a shallow valley formed by erosion which has cut through the till and exposed the underlying Jurassic limestone soils. Here, the 1824 map shows our first toll gate, Corby Toll Bar.(12) The road follows this valley, under the railway main line, past the second toll gate site at the junction with the Boothby Pagnel road (B1176), then down to the River Glen at Corby Glen, where it turns a little southwards to avoid more glacial till and keep to the upper Lincolnshire limestone.(13)