The rumbustious 1,000cc motorcycle, a Vincent Black Lightning, shone for a week this summer in the shopfront of Louis Vuitton, purveyors of leather goods to the rich and fashionable, before starring in a similar role at the upmarket Hurlingham Club.
The machine now belongs to HS Harris III, a giant but very gentlemanly lawyer, marksman and motorbike rider and restorer from Austin, Texas.
He has made the machine once again presentable, knowing that it has a fair entitlement to a party; just 50 years ago, on 13 September 1948, the Lightning charged across the Bonneville Salt Flats in Utah to prove itself as the world's fastest production motorcycle and the first to exceed 150mph.
The small and always struggling Stevenage factory from which the Lightning came took justified pride in making the world's fastest standard motorcycle.
Every successive post-war Vincent model - the Rapide, the Black Shadow and then the Lightning - had earned the title, and, if such things could be quantified, might also have been declared the world's best-quality and best-detailed motorcycle.
To Roland Free, who bought this first Black Lightning for immediate shipment over to the United States, the speed was attraction enough.
A racer before the war, and a Colonel in the USAF during it, he had returned to two-wheelers with a searing conviction that he ought to be faster than anybody else. He evolved his own riding style, which demanded that once the "bike was in top gear he should stretch himself out prone on the saddle, so as to present the minimum wind resistance".
Back in Stevenage, Mr Vincent himself - urbane Philip C Vincent, more a slide-rule engineer than a businessman - had calculated that the Lightning ought to reach 150mph on the salt, which would make it emphatically the fastest production motorcycle anywhere.
Try as he might to penetrate it, Mr Free (they called him Rollie) kept running into a barrier at l48mph.
Not at all a bad speed: fast, but not memorable. Wondering how he might grease the wind to better purpose, Free thought about the torn leathers he wore, and how they flapped in the wind.
Promptly he stripped: this time he would ride in nothing more than swimming trunks and sneakers. Bystanders shook their heads in anxiety as he set off; they applauded in relief as he returned.
He had done it. He had done 150. The record was won.
So, did he but know it, was 50 years of history.
There are production motorcycles now that can go a lot faster than 150mph, and the Vincent firm has long disappeared, like almost every other element in the British motorcycle industry; but the fastest man in swimming trunks may yet be Roland Free, and the machine he rode is still in good original condition, in good hands and in good health.