A further increase in performance of the engine, the concept of which dated back to before the Second World War, could no longer be achieved.

The key requirement was a six-cylinder configuration and a displacement of 3.0 to 3.5 litres, similar to that of contemporary Alvis engines.

However, the performance of the first prototypes was not convincing; in any case, the parent company was of the opinion that the financial expense of the new construction was not commensurate with its benefits.

This resulted in a displacement of 5.2 litres – with only a marginally changed stroke – as Chrysler did not have an engine of the appropriate size in its series portfolio.

The engine delivered an output of 250 bhp (186 kW) after the manual modifications, which more than doubled the performance potential compared to the previous model.

The switch to American engines was not without problems, although this step was not without a model: Facel Vega from France had already taken this route a few years earlier, and the British competitor Jensen was about to do the same.

The only changes were very subtle, comprising a single horizontal bar on the somewhat enlarged radiator grille, which had been steadily increased in size from the 405 to the 406 through to the 407, plus two exhaust pipes instead of one at the rear.

However, under the bonnet of the 407 was not the old BMW-derived six-cylinder engine that was now inadequate for Bristols to be able to compete in performance with other British makes of luxury car.

Replacing the old six-cylinder engine was a 5,130 cc (313 cu in) Chrysler V8, built in Canada, fitted with a new camshaft and mechanical tappets (lifters) of Bristol design.

[5] The bodywork on the 407 and subsequent models was built by bus body builder Park Royal Vehicles who also did trimming and finishing on some of those produced.

The new design had an elongated, rounded body with a very low belt line, a "hip swing" over the rear wheels and a lush glazed hatchback.

The car was significantly lighter than the factory 407 and reached top speeds of over 200 km/ h. The Bristol 407 GTZ Zagato was first exhibited at the Earls Court Motorshow in October 1961.

That wasn't just true for the radiator grille with a crest-shaped shield, which was borrowed from a Lancia Flaminia Supersport.

Tony Crook, who had initially hoped for a few orders, abandoned the project in the summer of 1962 because the plant could not resolve the weight distribution problems.