MG SV-R

But finally Auto Express has been invited to drive the most outrageous model ever to wear the octagon badge. We took to the track in the flagship SV-R which, at ΂£82,950, ambitiously aims to rival the likes of the Porsche 911 and Aston Martin DB9.

It's a bold quest from the British manufacturer, but one not entirely without substance. Under the bonnet of the SV-R lurks a V8 engine made of pure American muscle, and tweaked in Britain to deliver an astonishing 400bhp. The unit is based on that fitted in the ZT 260, but has been modified to deliver more than 40 per cent extra power. Those who are happy to live with fewer horses can choose the perfectly rapid 320bhp standard SV, and save ΂£17,000 in the process. But it's the SV-R which offers the more focused driving experience - and from the outside, this beast certainly looks as though it means business.

Inside, the car is a revelation. Given the low volume of the project, we were expecting an interior that was hastily thrown together from bits of old Rovers. We're pleased to say we were wrong - the SV-R has a hand-finished bespoke cabin, trimmed in leather and Alcantara, and the quality is much, much better than we had dared to hope for.

You know to expect serious performance as soon as you settle into the seat, because there's even a button to automatically lock the inertia reel of the four-point harness belts in place if you fancy some hardcore track driving.

And don't think the SV is an underdeveloped brute, either. It might have a proven V8 up front and a straightforward rear-drive powertrain, but it's bristling with technology. There's an on-board telematics system that automatically links with its own call centre to help customers with any problems, and it also detects when the car needs a service and calls the owner to inform them. MG Sport and Racing says this is essential, as SVs used for track days will need more regular maintenance.

And it's on the race circuit where the SV-R really shines. The V8 fills the cabin with a cacophonous roar, yet it's an easy car to drive at low speeds. Our main criticism concerns the traction control - when engaged, it takes over too quickly and saps power even under straight-line acceleration. Build up the pace and things become more interesting. The engine offers plenty of low-down grunt and power is fed to the wheels via a heavy but positive five-speed gearshift.

With the aero pack - standard on the flagship - this SV is apparently less likely to oversteer than versions without. But turn off the traction control and even this bewinged model feels twitchy. In the dry it's never uncontrollable, yet it's enough to keep you alert on the limit. The carbon fibre body gives the chassis more balance and allows greater steering precision, while the Brembo brakes are exceptional, with ABS that doesn't cut in until absolutely necessary.

It might not be the last word in refinement - in fact, it's a bit of an animal - but the SV will surprise those who didn't expect cash-strapped MG to turn out a such a well engineered supercar.