The B5348 is the former route of the A6 through Irthlingborough. The number presumably dates to the construction of the bypass in the mid 1930s, and is shown on the 1938 OS 1:10560 sheet.
The road turns southeast at the western end of the A6 bypass and becomes residential immediately. We follow the largely straight, initially tree-lined Finedon Road into town, the houses as expected becoming older the further we go. It's not long before we reach a roundabout with the market cross in the centre, where we meet the B571.
We now bear left along Station Road and become the junior partner in a multiplex with the B571. That turns off unexpectedly along Addington Road to the left so the B5348 regains its number by continuing ahead. We descend through an industrial area to return to the A6 at a roundabout.