The Princess 3Litre with its Vanden Plas designed frontal treatment was introduced in time for the October 1959 Earls Court Motor Show. Initially in Mark I guise the car was powered by BMC's 2912cc in-line 6 cylinder 'C' series engine which produced 108bhp at 4750rpm. A steering column change, 3-speed manual plus overdrive gearbox was standard with a 3-speed Borg Warner fully automatic available at extra cost. 

Apart from the frontal treatment the Princess received larger than normal rear overriders fitted directly below the rear lights. A stainless steel strip was fitted to each sill and distinctive hubcaps with central 'P' badges and chrome rimbellishers were fitted to each wheel. 

Internally the new Princess received the same treatment as the A120 and Wolseley 6/120.

In July 1960, the name 'Austin' was formally dropped from the title of Vanden Plas products which were thereafter marketed under the name of 'Vanden Plas Princess'. The Princess 3 Litre now became known as the Vanden Plas Princess 3 Litre.

In total 4715 Mark I's were produced before the model was upgraded to Mark II in October 1961.

The Vanden Plas Princess 3 Litre Mk II retained the same size engine but with a new cylinder head and improved air cleaner power rose to 120bhp at 4750rpm. A floor mounted gear lever was now fitted to manual cars. Externally the only difference from the Mark I was the fitting of a twin exhaust system and a small 'Mark II' badge on the boot lid. A 2 inch increase in the wheelbase was only discernible to the keen eye.

Internally the Mark II facia switches were redesigned, fresh-air outlets were fitted to the outer edges of the facia board, picnic tables were fitted as standard to the rear of the front seats and the seats gained adjustment for squab rake. Rear passenger legroom increased thanks to the wheelbase increase. The interior lights were also changed. 

In total 7901 Princess Mark II's were made including 7 estates (one for HM The Queen) and just one 2-door saloon made for Lord Kenilworth Chairman of Armstrong-Siddeley. Vanden Plas also produced a design for a 3 Litre 7/8 seater limousine. However the project got no further than the full-scale mock-up as shown pictured outside Kingsbury.