MINI Cooper S

Even as standard, the MINI Cooper S is an impressive piece of kit. But boasting 307bhp, nearly twice the standard car's output, it's simply mind-blowing. Few cars this small have ever been so fast. The conversion's £18,950 cost is clearly massive, but the results are so dramatic, it almost seems like real value for money.

Don't be fooled by the mild-mannered exterior. This MINI might appear familiar, but it eats Subaru Imprezas for breakfast and snacks on BMW M3s for lunch. It is the ultimate proof that looks can be deceptive.

Built by tuning expert Brodie Brittain Racing, this is a Cooper S like no other. With its supercharger junked in favour of a turbo, the BBR 300T pumps out a mighty 307bhp and 424Nm of torque. That's enough to propel it to a top speed of 160mph, and sprint from 0-100mph in the time it's taken you to read this paragraph.

Extracting so much power from the MINI's humble 1.6-litre engine takes a huge amount of work. Starting with a standard Cooper S unit, BBR strips and rebuilds it using a new cylinder head with bigger valves and polished surfaces to improve gas flow. The camshaft is replaced, and there's a new air intake and cooling system to force-feed the extreme motor.

Complex reworking of the electronic control systems and engine mapping is also required to enable the unit to run with a turbo rather than the supercharger. A three-stage throttle-actuated boost controller works to tame the 300T's rampant muscle. Naturally, it's not only the engine which has come in for attention. Fitted with BBR's own Power Grip suspension and uprated brakes from AP, the MINI's already capable chassis has been improved in an effort to cope with the vastly increased performance.

So, what does a 307bhp, 160mph MINI feel like? Explosively fast is the short answer. However, you need a steely nerve to guide it, for although essentially well mannered at modest speeds, the Cooper S 300T bares its sabre-like teeth when you push the throttle pedal to the carpet.

Under hard acceleration on the test track, the nose tugs and pulls at every bump and camber change, to the point where you need both (sweaty) hands on the steering wheel. Thanks to a limited-slip differential, wheelspin is kept in check to a remarkable degree, at least on dry roads. Once in fourth and fifth gears, the 300T's 100 per cent increase in torque ensures it surges forwards like an Impreza STi or Mitsubishi Evo.

Sadly, such performance does not come cheap. The full BBR 300T conversion costs £18,950 on top of the donor Cooper S - although the firm will be converting the first handful of cars at the special price of £16,000. However, if you want the ultimate giant-slayer, there's nothing else to touch it.