World's 'most important Aston Martin': Sports car that is just one of five ever made set to fetch £15m

The "most important Aston Martin ever produced" could become the most expensive British car sold publicly after it was given a £15million-plus price tag.

Aston Martin's 1956 DBR1 racing car is described as the firm's equivalent to the Ferrari 250 GTO and Mercedes-Benz 300 SLR.

Just five were built between 1956 and 1958 and this is chassis number one, a purpose-built model developed by racing design chief Ted Cutting.

DBR1/1 was designed to win at Le Mans, debuting at the 1956 race when Tony Brooks and Reg Parnell drove for 22 hours before suffering an engine bearing failure.

It was raced at two more runs at Le Mans in 1957 and 1958, the 12 Hours of Sebring in 1958 and 1959, as well as three entries at the Nürburgring 1000 KM, in 1957, 1958 and 1959, the latter of which saw an overall victory with Sir Stirling Moss and Jack Fairman at the helm.

The car did not ever win Le Mans, but another DBR1 did, and it was chassis number one that paved the way for the success and 1959 World Sportscar Championship victory - the first time victory for a British manufacturer.

RM Sotheby's has now announced it will be selling DBR1/1 over the weekend of August 18/19 at the Pebble Beach Concours d'Elegance.

Auctioneers have given the Aston Martin a guide price of "in excess of $20 million" (£15.6m) - potentially toppling the $21.8 million paid for a Jaguar D-Type last year.

It is part of a "once-in-a-lifetime group of Aston Martins" being sold at Pebble Beach, with a 1935 Aston Martin Ulster Competition Sports set to sell for £2 million and a 1959 Aston Martin DB4 GT valued at £6 million.

Barney Ruprecht, a car specialist at RM Sotheby's, said: "This is the most significant group of Astons to ever come to auction It is a true privilege to be entrusted with the sale of all four remarkable cars.

"From the Ulster - the pinnacle of pre-war competition - to the founding member of the DB4GT family, the ultimate Aston in the DBR1, all the way through to modern times with the DBR9, the group represents the complete lineage of Aston Martin competition history."

The Nurburgring victory marked DBR1/1's final appearance as a Works entrant, but it would return under privateer Essex Racing Stable in both 1961 and 1962.

It was then sold to the Honourable John Dawnay, future Viscount Downe and Aston Martin Owner's Club president, under whose ownership it saw considerable historic racing success in the early 1980s, piloted by veteran Mike Salmon.

The car passed through another major collection, during which time it was awarded the Most Elegant Sports Car Trophy at the 2001 Pebble Beach Concours d'Elegance, before landing with its current owner, who has not been named.

RM Sotheby's says it is the most correct of the five DBR1s built and while it has a new engine, it is being offered with its final Works-fitted engine. It is understood to be the first time a DBR1 has been sold at a public auction.