Britain’s history of eccentric, plucky sports cars has a newcomer this morning, from Aston Martin. Its bespoke Q division has taken the wraps off a one-off, 4.7-litre V8-powered rear-drive two-seater, the likes of which you’ve never seen before. Thought the Valkyrie was a tough engineering job, did you? Pah! Meet the Aston Martin Cygnet V8.

This isn’t some half-scale model-shop V8 either. Oh no. Aston has shoehorned the 4.7-litre, 430bhp naturally aspirated V8 from the last-gen Vantage S under the barely-there bonnet of the Toyota iQ-based Cygnet, and sent drive – via a tiny torque tube – to the rear wheels.

Speaking of wheels, they’re up from piddly 16s to meaty 19-inch rims, encasing beefy brakes and almost bursting from the Cygnet’s diminutive bodyshell. Hence, carbon-fibre wheelarch extensions. Of course.

Much of the Cygnet has needed a fiendishly complex – and expensive-sounding – rehash to accommodate its new 430bhp heart. Front and rear subframes are derived from the same Vantage as the engine, while there’s an entirely new front bulkhead, transmission tunnel (just look at that handbrake) and a racey part-Vantage interior, complete with roll cage and bucket seats.

At the back, Aston’s fabricated a bespoke exhaust system, which lives directly below the steel fuel tank. And yet, not only is the car completely road legal, Aston says it’s not far off being FIA motorsport certifiable. One-make race series, anyone? It’s about time Formula One had an interesting feeder championship.

Adding a V8, a seven-speed automated manual gearbox and associated beefy ancillaries to a Cygnet has had an effect on the weight, despite the stripped-out cabin. Aston says the finished project weighs 1,375kg with fluids, compared to the base car’s 920kg.

And yet, thanks to a 313bhp per tonne power-to-weight ratio, Aston’s claiming a mildly terrifying 0-62mph time of 4.2 seconds, and a top speed of 170mph. Bet that’s lively, with a wheelbase barely longer than the door itself. Small wonder Aston had to install the 380mm/330mm brakes of the Vantage donor car to rein the super-Cyg back in…

Not so much a pocket rocket as a microscopic missile, the V8 Cygnet will be bringing its own brand of miniscule fury to the Goodwood Festival of Speed this weekend. Blink and you’ll miss it. Keep your eyes open and you still won’t believe them. It’s what makes Britain great, isn’t it?