till soil that we start our journey. Bourne Road, Colsterworth, the section removed from the A151, remains part of the B676, the road which leads westwards, towards Melton Mowbray. Once the clutter associated with a trunk road junction is left behind, the road passes through agricultural land and woods. To the north are fairly level fields and to the south, Twyford Wood, which cloaks the remains of North Witham airfield. Corby Glen 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. 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. The land between Colsterworth and the western edge of Bourne is a plateau, gently sloping down to the east and much dissected by erosion during periods when it was near but not under ice caps. The River Glen which we crossed at Corby Glen is also called the West Glen and is in one of the two main dissecting valleys. East of Corby Glen, we are on a strip of un-dissected plateau. The surface dips very gently towards the east but the geological strata dip more steeply so that a kilometre out of Corby Glen, the road passes onto the strata above the limestone, known as the Upper Estuarine Series, the Blisworth Limestone, Blisworth clay, Cornbrash and Kellaways clay, in that order. Edenham At Irnham crossroads, the A151 leaves Corby Glen parish for that of Edenham and is back down on the cornbrash. To the north, unseen in its little valley beyond the woods is Irnham, once the home of Sir Geoffrey Luttrell, who commissioned the Luttrell Psalter, a book which tells us so much of English everyday life in the 14th century. The road dips into the valley of the stream which flows on to form the lake in Grimsthorpe Park. Just skirting the glacial till, it rises to the crest at the other side, on the Kellaways clay and sand