As the road arrives back on the Jurassic clay, it meets the A6121, a road designation which ends here, having begun at Morcott, in Rutland, on the other side of the A1, hence its beginning with the digit 6. In 1824, there was a toll gate here.(20) The course of the A151 is directly down the slope into Bourne. It is clear archaeologically that the road used to run parallel with this and about 200 metres to the south. Historically, there appears to be no commonly available record as to when the move was made. It was certainly in two stages. The move of the upper part was probably made in the 18th century; the lower, in about 1140, when Bourne castle was built across it. Its present course is dictated by the former presence of Bourne Castle at the town end and by a desire to keep to the crest of a slight ridge in the hillside.(21)