The Marina was developed under the ADO28 codename. The impetus for its development came when Leyland Motors merged with British Motor Holdings (BMH) in 1968, thus forming British Leyland. BMH was the corporate parent of the two biggest car manufacturers in the UK, Austin and Morris. The new BL management, made largely from ex-Leyland Motors staff, were shocked to learn that apart from the Austin Maxi (then entering the final stages of development) and a tentative design for a replacement for the Mini (the 9X) BMH had no new cars under development. The company's products aimed at the mass-market consisted of the Morris Minor, dating from 1948, and the 1100/1300 range of mid-sized Austin and Morris saloons that were a decade old. BL rapidly implemented a plan to develop a replacement for both the Minor and the smaller Farina models that could be produced as quickly as possible and would be on sale for no more than five years until a genuinely "all new" product could be launched in its place.