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jaguar4 min read·11 Jul 2026

1950 Jaguar XK120 — Auto Friday No. 109

BattlePorQRM Sotheby's

Friday again. Out of nowhere. Wasn't expecting it back so soon.

Since I brought up postwar European — and specifically British — sports cars in the recent thread about the Chevrolet Corvette's birthday, today's post might as well be about one of them. Probably the most famous one of all.

Before the war, Jaguar — or SS Cars Ltd., as the company was still called back then — powered its cars with engines bought in from Standard, heavily reworked in-house but outsourced all the same. Civilian production naturally had to stop for the duration of World War II, but work on the company's own next-generation engine began at SS as early as 1943. In 1945 the name was changed to Jaguar — the SS initials had picked up some rather unpleasant associations — and production of the prewar models resumed under the new name. Not an entirely new name, mind you: 'Jaguar' had been a model in the SS lineup since 1937. Meanwhile they were preparing all-new cars around the all-new engine: after experimenting with four- and six-cylinder units, they settled on a 3.4-liter DOHC inline-six. The company saw its core market as substantial, stately saloons with a light sporting flavor. But things didn't quite go according to plan.

To test the new engine, in 1948 they knocked together — in just six weeks — a test chassis wearing a strikingly handsome open two-seater body, penned from a sketch by company founder William Lyons. In October 1948 it appeared at the London Motor Show as a promotional show car, the idea being that if there was any interest, they could perhaps build a couple hundred for sale. Without hurting the big, expensive, respectable saloons, of course.

Except the XK120 — built with prewar methods (a wooden body frame with aluminum outer panels) and utterly unsuited to mass production — turned out to be a sensation. A queue of buyers formed literally on premiere day (something similar happened with the first Corvette a little later, by the way), and to seize the moment the company had to improvise what was essentially semi-handbuilt production of the new, now-series model.

From late 1948 to early 1950 they managed to build 242 Jaguar XK120s with wood-and-aluminum bodies, after which, to simplify production, they switched to an all-steel structure and built another 12,000. It's those early cars — the so-called Alloy XK120s — that are the most prized by collectors today. Back then, though, this was a chance to buy the fastest production car in the world for just £998. The '120' in the name stood for the guaranteed top speed in miles per hour — 193 km/h. In practice, test runs saw production cars reach 132–133 mph, and in 1950 one lapped the Montlhéry circuit in France for 24 hours straight at an average of just over 120 mph.

The XK's full story is long and fascinating, and the XK engine's story is longer and more fascinating still — it stayed in production in various forms all the way until 1992. You could write a book about it. What we have here, though, is just a modest set of 24 photos, courtesy of RM Sotheby's. So enough talk — let's look.

2. This car went on to define Jaguar's instantly recognizable house style for a long time to come.1 / 48
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9. Sitting in here doesn't look all that comfortable, if you ask me.8 / 48
10. Or would 'lying down' be the more accurate term?9 / 48
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15. And here it is — the Jaguar XK engine. An inline-six with twin overhead camshafts and hemispherical combustion chambers; cast-iron block, aluminum head. In this original 3.4-liter twin-carburetor form it produced 150 hp at 5,000 rpm, with peak torque of 264 Nm at 2,500 rpm.14 / 48
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18. Top speed around 200 km/h, 0–100 km/h in 10 seconds.17 / 48
19. That said, with a little fettling cars would do 210–220 km/h and hit 100 in just over 8 seconds. Factory versions with 180–220 hp followed soon after.18 / 48
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23. Wouldn't say no to this right now, instead of... well, all that.22 / 48
24. So there you have it — a quick rundown of something that really deserves the full-length treatment. That's all for now.23 / 48
The very first prototype, assembled back in the summer of 1948, looked noticeably different from the future XK and was simply called the Jaguar Super Sports.24 / 48
Still, the outlines of the future XK120 are already visible.25 / 48
And this is the very first XK120, serial number 660001 — the actual car shown in London.26 / 48
Today's Jaguars are a different story altogether. Not an interesting one. )) 1949 Jaguar XK120 Alloy Roadster #67006027 / 48
1949 Jaguar XK120 Alloy Roadster #67005928 / 48
1952 Jaguar XK 120 SE Fixed Head Coupe29 / 48
1953 Jaguar XK120 SE30 / 48
And this is the Mark VII saloon — the car this whole venture was actually meant to serve.31 / 48
...32 / 48
Well, the whole world is sliding into a rather dark abyss these days — hard to expect any one corner of it to be spared...33 / 48
The XK150 (1957–61), the last of the XK line. In its most serious versions: the 3.4 with 250 hp and the 3.8 with 265 hp.34 / 48
The XK120 and the electric i-Pace.35 / 48
The complete kit.36 / 48
The first XK120s were aluminum mainly as a matter of economy: in postwar Britain, rationing covered not just food but scarce sheet steel too, while aluminum was plentiful after wartime aircraft production wound down. The Land Rover, incidentally, got its aluminum body for exactly the same reason. The XK120 LT cars purpose-built for Le Mans, though, used aluminum bodies for genuine weight savings. Pictured is a replica built on a 1954 car.37 / 48
Right — you can tell from the proportions, and especially the wheels, that it's not an original. The real XK140:38 / 48
1952 Jaguar C-Type. The racing car developed from the XK120 was first called the XK120C, later known simply as the C-Type. A tubular spaceframe instead of the ladder chassis, the 3.4 tuned to 200–220 hp — and two Le Mans victories.39 / 48
The next step in its evolution — the 1954 Jaguar D-Type.40 / 48
An XK120 with Pininfarina bodywork.41 / 48
Inside.42 / 48
The last car to carry the Jaguar XK engine under its hood was also the last classic British limousine — the Daimler DS420, built on the Jaguar Mark X platform and produced until 1992.43 / 48
A 1952 XK120 (672282) that belonged to Clark Gable.44 / 48
In 1951 the coachbuilder E.D. Abbott of Farnham produced a one-off four-seat XK120 convertible.45 / 48
The jack in its proper place, next to the spare wheel:46 / 48
A tough choice. The Mark II is a fascinating car in its own right — they're just very different animals.47 / 48
Clark Gable, William Lyons and the XK120.48 / 48

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