The B4643 is a short B road to the south of Chippenham, following a short section (between the B4528 and A4) of the original line of the A350 out of the town. That road was first diverted onto the present B4528 route, before taking up its current line around the western bypass. This short stretch of the old route seems to have been either a spur of the B4528 or an unclassified road for a while, before assuming its current number in the 2010s. It has also erroneously been marked as the B4634 on some maps.
