Featuring the legendary styling of aerodynamicist Frank Costin, number six was the Costin works car and arguably the ‘most famous’ of the nine. It was driven by several top drivers of the period, including the legendary Gerry Marshall who won at Thruxton in 1971, as well as by Brian Hart and Paul Pycroft de Ferranti in a three-hour 1971 race at Le Mans.

The car is fitted with its original Blydenstein 2.3-litre Vauxhall dry sump rally specification engine, with split-circuit braking system and a Getrag five-speed gearbox with limited slip differential. Sitting on Carmona alloys, it also features the special air intakes fitted for the Le Mans race.

'This stylish and rapid machine guarantees an invite to significant race and concours events, and will appeal to any racer, or road driver, who wants to stand out from the crowd,' said Silverstone Auctions’ Guy Loveridge. 'One of the most iconic car designs of its era, it carries many style elements from the automotive industry at that time, and is considered to be one of Frank Costin’s greatest designs. In light of its unique heritage, this remarkable car should comfortably reach around the £70,000 mark and our auction event on 23 July, during the Silverstone Classic weekend, provides the perfect environment in which to present the car for sale.'

The 137 mph (estimated) car was built in Little Staughton, Bedford, by Marcos co-founder Frank Costin, brother of Cosworth co-founder Mike Costin.

The car was sent to Bill Blydenstein by owner Paul Pycroft for a total rebuild in the 1980s, which has been extremely well documented. It has a top quality fitted car cover suitable for towing, full MSA historic technical papers and barcode, and is fully UK road registered with an MoT.