Built by Blue Boar, operators of the first MSA at Watford Gap, and originally known as Rothersthorpe Services. The site was completely rebuilt by RoadChef when they took over.
As constructed, Rothersthorpe was an "online" services in between junctions, but there was so much traffic using the MSA via the rear entrance to reach the A43 that eventually a junction (15A) was constructed to allow this to be done legitimately. This has resulted in a slightly convoluted junction layout which effectively wraps around the outside of the services, which can still be accessed directly from the M1 rather than, as with most junction-located services, via a roundabout.
Northampton Services M1 is a 3 burger rated service area.