The Austin Princess IV DS7 was introduced in 1956 to replace the Princess III DS5. It was very different from the earlier A135 Princess saloons. Once again the car was designed and built by Vanden Plas. The bodyshell  was made of steel with aluminium used for the bonnet and boot lid to save weight. The boot lid was now hinged at the top (rather than the bottom hinges of the earlier cars) and was spring loaded, and the bonnet was hinged at the rear and opened at the front together with the large radiator grille making it rather heavy.

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The wheelbase was increased by 2 inches to give extra passenger room.

Mechanically the car was powered by an uprated 'D' series 3995cc engine with redesigned cylinder head. Fitted with twin S.U. HD6 carburettors power increased to 150bhp. A General Motors Hydramatic automatic gearbox and Girling power-assisted steering were fitted as standard.

The sumptuous interior now contained a redesigned facia with the principal instruments sighted in front of the driver rather than in the centre.

  

In 1958 the car lost its Austin name being renamed the 'Princess IV'. The 'Flying A' was deleted from the radiator grille and replaced by a Coronet badge. The hubcaps were also altered to ones containing a central plastic badge with a 'P' for Princess motif.

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Only 175 saloons (DS7) and 24 Touring Limousines with glass division (DM7) were produced before production ceased in May 1959. This was to prove to be the last of the big Princess A135 saloons.