According to an interview with Sir William in the 1970s, the design was
created, start-to-finish, in less than three weeks

The first post-war auto salon held in London, the Earls Court British Motor Show, opened its doors on October 27, 1948. No one was prepared for the shock caused by the unveiling of the bronze-colored Jaguar roadster, the XK 120. William Lyons raised the bar for sports cars with this model, and nearly 60 years later we still admire its superb lines and the sound of its inline six-cylinder motor.
The XK120 entered into production in 1949, and was instantly in high demand. The first 244 XK 120s-including the car on offer here-were clad entirely in aluminum. In period, these represented the best of the best, with their advantageous power-to-weight ratio courtesy of the alloy body and the highly tunable, dual-overhead-cam XK engine. This engine was used in production Jaguars in successive stages of development through 1987.
Like many of its siblings, this XK 120 was first shipped to the United States' West Coast, where it was campaigned in a number of amateur sports car races at Monterey and Santa Barbara. It then served for a time as a dirt-track racer, fitted with an American V8 engine when its original gave out. In poor condition, it returned to England for a full restoration by John May of XK Development at Homesdown Farms, Fiddington.
The car has been prepared according to the Historic Sports Car Club rules, with respect to the spirit of 1950s-era racing. The drum brakes have been kept, as has the steering box (which has been displaced to the right side). Even the lever-arm shocks have been kept at the rear. The engine has been tuned with specific camshafts, 9:1 compression ratio, a C-type head, and SU HD8 carbs, and the Moss gearbox is of the close-ratio type.
Finished in pearl grey with red and biscuit interior and two aero screens, this Jaguar wears red wire wheels and is described as being in very good working condition. It is eligible for many historic events, including the Mille Miglia, Tour de France, and Le Mans Classic.

SCM Analysis


Vehicle:1950 Jaguar XK 120
Years Produced:1949-50
Number Produced:240
Original List Price:$3,945
SCM Valuation:$105,000-$145,000
Tune Up Cost:$650
Distributor Caps:$45
Chassis Number Location:front of left-hand chassis side member
Engine Number Location:right-hand side of cylinder block above oil filter
Club Info:Jaguar Clubs of North America, c/o Nelson Rath, 1000 Glenbrook, Anchorage, KY 40223
Alternatives:1953-55 Aston Martin DB2/4 DHC, 1955 Austin-Healey 100S
Investment Grade:A

This 1950 Jaguar XK120 roadster sold for $179,200 at Artcurial’s Paris sale, held on February 13, 2005.
There can be no question that the introduction of the prototype XK120 in October 1948 was one of the great automotive success stories after World War II.
It is often told how William Lyons and his key managers had used their time during wartime factory fire watches to define preliminary plans for the twin-overhead-cam, straight six-cylinder engine that would become the linchpin of Jaguar’s post-war development. As soon as hostilities ceased, those plans were put into development and by late summer of 1948, the new engine was ready for introduction.
There was only one problem-the sedan for which it was designed wasn’t ready to be shown. Instead, Jaguar’s Mark V, still employing the prewar 2.5- and 3.5-liter engines but with a stylish body design, was to be introduced as the firm’s primary offering. So to showcase the new engine, Lyons decided to create a limited-production sports car that would draw attention to Jaguar’s sedans.
Lyons started with the chassis of the Mk V, with its new independent front suspension and hydraulic brakes, and cut 18 inches out of the center to produce a 102-inch wheelbase. Over that heavy chassis, he sculpted an aluminum body with a long tail, set-back seats, and fenders that swept forward from the base of the doors in voluptuous curves, to nearly meet under a slender grille integral with the long bonnet.
According to an interview with Sir William in the 1970s, the design was created, start-to-finish, in less than three weeks. Of course, we can assume that Lyons began with the basic proportions of the pre-war SS100 coupe prototype. Design elements from the pre-war Alfa roadster and BMW 328 are certainly suggested as well.
Regardless, demand for the XK120 Super Sport was so much greater than Lyons had anticipated that Jaguar immediately began to tool up to produce the car in steel.
In the meantime, an alloy-bodied XK120 roadster was taken to the Jabbeke autoroute in Belgium in May 1949, where, in the presence of the auto press, it was timed at 126 mph in street trim, more than justifying the 120 of its name. A few weeks later, that same car won Britain’s first post-war motor race at Silverstone. Jaguar was well and truly into the sports car business.
While the tooling was being completed for the steel cars, Jaguar continued to produce a trickle of alloy cars before the steel bodies took over production in early 1950. Aside from the body panels, only a few details, such as the straight windshield pillars, distinguish the alloy cars from their successors.
Today those alloy body cars are the most coveted of the XK series, and typically fetch twice the price of comparable steel XK120s. This certainly explains part of the premium paid for the car pictured here. Yet still, the sale price for this particular car seems well above what one might have expected. The SCM Price Guide lists the value range for aluminum XK120s at $105,000-$145,000, with the steel ones in the $45k-$70k range.
In particular, in a marque that places great stock in matching numbers, this 1950 XK120 roadster has a replacement engine. Having been the subject of heavy track use (on dirt even), it’s not inconceivable to assume that many of the trim pieces are not likely to be original to the car. This seems to be a well-weathered warhorse that has survived this long only because someone was careful enough to keep the body number plate and chassis number intact.
Granted, an alloy-bodied Jaguar in racing trim is indeed eligible for many vintage events, but if one is looking for an early-1950s vintage car to race, there are many alternatives that might have been purchased for the same price, including an Aston Martin DB2/4 DHC or an Austin-Healey 100S.
Let’s just chalk the high price here up to the weak American dollar, and hope that the buyer was paying in Euros. Even then this was hardly a bargain.
(Descriptive information courtesy of the auction company. Additional translation by Kristen Hall-Geisler.)

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