The original 400 Series, launched as a four-door saloon in early 1990, was simply a saloon version of the "R8" 200 Series hatchback, and like the 200, was based on the Honda Concerto. It used the same core structure and mechanicals as the Honda, but the rear-end redesign of the glasshouse and structure was unique to Rover, there being no Honda UK equivalent. Interior trim and electrical architecture were all carried over from the core, 5-door, vehicle.
An estate or station wagon version, the '400 Tourer', was subsequently developed by Rover Special Products, based on the extended floorpan of the 400, offering an alternative to the "sports touring" BMW 3 Series and Audi 80 small estates that had become increasingly popular, a first attempt to move Rover Group estate cars away from the utilitarian end of the market.
The diesel powerplant was supplied by PSA Peugeot Citroën in 1.8 turbodiesel and 1.9 normally aspirated configurations. Petrol Models made first use of the Rover K series engine (along with the MkII 200) in 1.4 litre form. 1.6 L models were powered by the Honda D series engine in both single cam and twin cam versions. 2.0 litre models were powered by the Rover T series engine in both normally aspirated and, in a limited run, turbocharged form giving rapid performance.