Complex sentence: AP also developed a close technical partnership with the British Motor Corporation (BMC), one of the most notable products of this collaboration was the unique AP automatic transmission used in the Mini and later BMC/BL compact models.
Split into simpler sentences: AP also developed a close technical partnership with the British Motor Corporation (BMC), in the development of automatic transmissions. One of the most notable products of this collaboration was the unique AP automatic transmission used in the Mini and later BMC/BL compact models.