Complex sentence: H. J. Mulliner & Co. is a well-known British coachbuilder who traces their history to 1760, building coaches for the Royal Mail in Northampton.
Split into simpler sentences: H. J. Mulliner & Co. is a well-known British coachbuilder. The Mulliner family can trace their coachbuilding history back to 1760, building coaches for the Royal Mail in Northampton.