One-of-ten Ariel Atom Mugen for sale

British sports car makers have rarely made fast cars the way manufacturers from other countries do. Lotus, as you know, turned the racing and sports car world on its head by prioritising lightness, not power, in its pursuit of performance. Many decades later, Noble burst onto the scene with the M12, a homemade rocket ship that gave all but the fastest, most unobtainable supercars a run for their money. Around the same time, a little company called Ariel came along and altered our perception of what a lightweight track car could be. 

Or any car, for that matter. Because the only thing separating an Atom from a motorbike was an extra pair of wheels, a brace of seats and a steering wheel. The Atom’s tubular chassis doubled up as the exterior body, with the suspension, engine and cockpit all exposed to the elements. Various powertrains have been offered over the past 25 years, but the Atom really came into its own when it switched to Honda power. As you’d imagine, a Civic Type R engine strapped to some scaffolding was utterly bonkers, screaming to a sky-high redline while the wind rearranges your face. And because anything with a Type R engine usually attracts Honda specialists Mugen, it was only a matter of time before the Japanese tuner got its hands on it.

Built as a ten-year anniversary gift to Ariel, the Atom Mugen might just be the very best of its naturally aspirated cars. Using the legendary 2.0-litre K20 engine, Mugen set about dialling the power up with upgraded pistons and valves, racier cams and motorsport-grade spark plugs. That brought the Atom up to 270hp, which, granted, was only a 25hp bump on the standard car, but when you consider that’s 135hp per litre from an engine free from forced induction, it just shows what Mugen – and the K20 – are really cable of. 

Work then turned to the chassis, which featured the suspension and limited-slip differential from the one-off V8, chunky Alcon brakes for even more ferocious stopping power, plus a close-ratio six-speed gearbox and a lighter flywheel. A kerbweight of 550kg isn’t hard to believe (there’s not much here to weigh it down), but its 490hp-per-tonne power-to-weight ratio and a 2.9-second 0-62mph time should give you an idea of the lunacy that awaits.

Happily it does without the questionable bodykit that traditionally comes as part of the deal with a Mugen tune (because, again, where would you put it?) though the red scaffolding and white wheels serve as a neat tribute to the Atom’s Honda connection. Only ten were produced, though this one’s believed to be the only example that’s been built to Atom 3.5-spec, which, if you really know your Ariels, was obvious from the newer headlight design.

It may just be the rarest Ariel production model, if you take the bespoke V8 and the soon-to-be-released Hipercar out of the equation. To get your hands on it, you’ll need a spare £49,950 and, preferably, a free weekend to enjoy it, because there are only 739 miles on the clock. Those are rookie numbers, especially for a quicker version of one of the best two-seat sports cars to come out of the drizzly island we like to call home. Anyway, it looks like we’re in for a hot one this summer, and this seems like the perfect way to make the most of it.