The Rover P4 series is a group of mid-size luxury saloon cars produced by the Rover Company from 1949 until 1964.
Their P4 designation is factory terminology for this group of cars and was not in day-to-day use by ordinary owners who would have used the appropriate consumer designations for their models such as Rover 90 or Rover 100.
These cars are very much part of British culture and became known as the 'Auntie' Rovers. They were driven by topmost royalty including Grace Kelly.
The P4 series was supplemented in September 1958 by a new conservatively shaped Rover 3-litre P5 but the P4 series stayed in production until 1964 and their replacement by the Rover 2000.