Church Street, Wellingborough
The A5128 is a replacement of the original routes of the A510 and the A45 through Wellingborough before the bypass was built.
The road starts just west of a bridge over the Midland Main Line where the A510 turns right at a mini-roundabout onto Wellingborough's northern bypass. The A5128 continues ahead along that road's old route. The road runs along the residential Finedon Road, crossing a roundabout where it meets the B573 before bearing left into Cannon Street to reach the town centre's one-way loop.
Westbound traffic continues along Cannon Street, which remains two-way. After passing Aldi a set of traffic lights is reached from where the B572 heads west and the A5128 TOTSOs right. The road quickly bears round to the left into Castle Way and finally becomes one-way itself. We pass a multi-storey car park to reach traffic lights on the A5193, which is the original route of the A45. Here we bear right and head north along Sheep Street, soon reaching the turn for Oxford Street on the left; this is the western continuation of the A5128 but the loop continues ahead into the High Street. A5128 traffic must keep in the right-hand lane (left is for the A5193 which soon branches off) to bear right into Church Street. After passing the church, the road bears left then right into Alma Street, which leads back to the end of the loop at the traffic lights on Cannon Street.
Returning to Oxford Street, the A5128 now heads west through the suburbs. There are two mini-roundabouts by a small park and we bear slightly left at the latter. The road then continues along Northampton Road. After passing a Sainsbury's on the edge of town, the road ends at a roundabout on the A509 western bypass. The road ahead is the A4500, emphasising that this is the old A45.