The B1507 followed the pre-bypass A10 through Downham Market. The road dates to the construction of the bypass in the 1980s but had been declassified by 2000.
The road originally started at the southern end of the A10bypass and headed north through Denver to reach the A1122 southern bypass. Some maps claim that following construction of the A1122 the B1507 was cut back to have its southern end on this road, although other maps disagree.
To the north of the A1122 the B1507 headed north along Downham Road into the town centre, where it ran along Church Road and crossed the B1512 at the northern end. After leaving town along Lynn Road it skirted the edge of Wimbotsham before returning to the A10 on the edge of Stow Bardolph.
Most signs have been patched over for the B1507 due to its declassification. However as of 2016 there are still at least two signs for it in existence. One is on the staggered crossroads with the A1122 on the southern exit of Downham Market. The other can be seen in the town centre on what used to be the B1512.