The Classic TT is a place where you can realise your maddest mechanical dreams. Royal Enfield fanatic Steve Linsdell has already achieved one, only halfway through practice week, by building a 500cc single-cylinder bike based on a pushrod 1950s ride-to-work machine, that's cracked 140mph through the Sulby Straight speed trap.

Steve believes that that's quicker than any of them upmarket overhead-camshaft Manx Norton and Matchless G50s have ever gone on the blast down towards Sulby Bridge.

And this with a Royal Enfield, a make with almost zero TT course pedigree. “I wanted to build a bike that was all Enfield,” says Steve, who used to bob about on a 350cc Enfield Bullet single when he was a lad. “I've used an Enfield frame, forks, and swinging arm, and all the castings are original. The cylinder head, timing case, crankcases, gearbox casing - it’s all original old stuff.”

The gearbox shell is packed with a Nova six-speed cluster, the carburettor is a 41mm Dell’Orto, and there's a Seeley front hub and a single disc brake. A sort of double-panel fairing guides air around the cylinder head and barrel. But to continue the Enfield theme, the rear seat moulding is based on that of the 250cc Royal Enfield GP5 250cc two-stroke single racer of the 1960s, and the fuel tank shape comes from the 250cc Continental GT cafe racer.

Steve’s treated his motor to a well over-square bore and stroke ratio of 90 x 78mm, and reckons he's got more than 50bhp in there. More surprisingly, his son Olie is told that it'll rev safely to 8400rpm - that's getting on for short-stroke G50 territory.

Steve and Olie, who've been punting Enfields round the Mountain Circuit for a few years now,  had another dream coming into this Classic TT - to beat the overhead-cam jobs to be the first 500cc classic single to set a 110mph lap. But Olie dislocated a shoulder a couple of weeks ago and isn't yet fully sharp. The ton-ten fantasy might have to wait for another year.