The XKSS was a happy accident from Jaguar's decision to withdraw from racing after the 1956 season. As a result, Sir William Lyons decided to convert the remaining D-Type race cars into high-performance sports cars. Known as the XKSS, Jaguar built 16 examples including this one, XKSS 707, which will be auctioned by RM Sotheby's during Monterey Car Week in August.  

Originally painted cream over red leather, XKSS 707 was purchased by Lou Brero Sr., who died in a racing accident before he could take delivery. The car was instead sold to Sammy Weiss, owner of Oxford Motors in Sacramento, California, who sold it to Sidney Colberg. The car remained in Colberg's collection until he sold it to Lord Anthony Bamford in 1975. 

Lord Bamford, who is chairman of JCB, a British heavy equipment manufacturer, owned it briefly before passing it on to Geoffrey Marsh, who had it reconditioned before passing it on to I.G. Campbell McLaren. It was McLaren who had XKSS 707 refinished in metallic blue and registered it with the JAG 1 vanity plates it wears today. The car remained in the McLaren stable for years, continuing to compete in historical events like the Le Mans Classic, and was featured in several British enthusiast magazines.

Gallery: Jaguar XKSS 707 RM Sotheby's Auction

 In 1992, it was purchased by Allen Lloyd, who discovered the car no longer had its original engine block. Lloyd enlisted the help of Chris Keith-Lucas, an authority on competition Jaguars, who tracked down the original engine block and reunited it with the car. XKSS 707 remained in Lloyd's care for 19 years, where he drove it in the historic 2004 Mille Miglia and exhibited it at the Jaguar Heritage Museum at Browns Lane. 

XKSS 707 is perhaps the best-documented model of the series with 25,535 miles on the odometer. It also retains its original serial number plate, chassis number, engine, and gearbox. Next month, it will be featured at the RM Sotheby's Monterey Auction, where it is expected to sell for over $12 million (approx. £9.3 million).  

The Jaguar XKSS and the D-Type it's based on were cutting-edge supercars of their day, much like a modern McLaren Solus GT or Aston Martin Valkyrie. They rarely come up for sale, but in addition to XKSS 707, RM Sotheby's is auctioning a Jaguar D-Type during Monterey Car Week, which you can currently view on the duPont Registry.