Taken from the Motor October 15th 1929
The Arthur Mulliner Main Service Department at Northampton. With a wide frontage to Bridge Street and Cattle Market Road , Mulliners main service department is under the personal suoervision of Mr. H. E. Road, who is well known throughout the trade as one of the finest service experts in the country. Previously he has been associated with Messers Murkett Bros. Messers Brainsbury's and later upon his own account at Reads Garage Peterborough, before joining Mulliners, and his advice upon all matters of service to the trade and car users in general is freely offered.

Taken from a small sales brochure of Mulliners.
Is this definitely in Bridge Street as it doesn't match any other images we have seen

However after searching adverts from the early 20th century this image was found which shows this building to be standing between the plough hotel and St Johns