The B2021 cuts the corner between the B2260 (former A21) and the A227 (former A26) in Tonbridge. Because the officially signposted route for through traffic on the A26 is signed down the A2014 to the A21 and back around the east of the town, it is often quicker to use this route, in conjunction with the B2260, to head through the town. However, the western end of the road is narrow and therefore one-way towards the B2260.
The B2021 originally ran along Bordyke
Originally, the B2021 used to run on Bordyke, cutting the corner between what was then the A21 and A26. The B2021 and A26 swapped in the 1950s, giving the B2021 its current route. The A26 was rerouted to the east of Tonbridge in the 1990s, so the original route of the B2021 is now part of the A227.