If the Sixties were about experimenting, Alec Issigonis and John Cooper were the men in motoring who laughed in the face of the rulebook. Kicking constraints into touch and starting afresh, Issigonis made an international success out of his ever-so British brainchild, the Mini. But it was only when he paired up with Cooper, the Formula One race-car designer, that the true magic shone through, in the brilliance of the 1961 Mini Cooper.

Transforming the original Mini from tiny to tearaway, the souped-up super-Cooper won the public’s adoration. Here was a car that could out-corner Ferraris for a factory-floor wage packet. Little wonder that from the decade that spawned more British stars than any other, the Mini Cooper is up there with Carnaby Street, Mary Quant and the Beatles. It took the leading role in The Italian Job and was owned by some of the coolest people on the planet — Steve McQueen and Enzo Ferrari included.

Today, neither Issigonis nor Cooper is present to witness the launch of the Mini Cooper JCW (standing for John Cooper Works), the fastest, most powerful Mini Cooper to date, and the first to be put into unlimited production with a price tag greater than £20,000. In fact it costs £20,995, a startling £4,750 more than the turbocharged Cooper S on which it is based.

But look at what that buys you: an engine with 211bhp instead of 175bhp, a reduction in 0-62mph time — from 7.1 to 6.5sec — and a top speed that has increased from 141mph to 148mph. In addition, there’s a new body kit, air-conditioning, a strengthened gearbox, an electronic differential to help handle the extra power, and some bespoke John Cooper Works badges.

Sounds promising, doesn’t it? This could just be one of the most exciting cars to hit the road since . . . well, since the original Mini Cooper handbrake-turned onto the scene. Sadly, though, the reality is anything but. Instead of being the best sporting Mini ever created, it is the least appealing I’ve driven.

There are a few small problems you could overlook: the interior is barely distinguishable from that of the standard Cooper S, the new badges look cheap, and in the quest for more visual “attitude”, the body kit spoils the Mini’s pert lines.

These, however, are mere niggles. The real issue is that this Cooper leaves a smile missing from your face. What Issigonis and Cooper’s original concept cracked so successfully was the blend of modest power with maximum thrills. Unfortunately, the Cooper JCW doesn’t continue that formula.

Faced with the typically bumpy B road on which British customers will want to exercise the car, the JCW feels overwhelmed by its power. Yes, it feels engagingly sporting, because even the standard suspension is very stiff (goodness knows what the lower and yet stiffer optional JCW sports suspension would feel like) and the steering is quite aggressive, giving large changes of direction for very small inputs. But this novelty soon wears off, and what’s then left is the overwhelming impression of a car with an engine that provides a greater workload than its chassis can deal with.

Every time you try to drive the JCW the way its looks and specification beg you to, the front tyres struggle to maintain traction and the nose tugs unnervingly from side to side.

If you leave the electronic driver aids engaged they will smooth off some of the rough edges. But at the same time they also deny you access to large chunks of that extra power you’ve spent so much money on. Turn off the aids and the way the front wheels kick, skip and buck is worrying.

In the end, I got so tired of being bounced around in my seat, constantly correcting the steering and trying to modulate the throttle to minimise the worst effects of the torque steer, that I decided to take the easy option and simply slowed down. And that’s enough to have John Cooper turning in his grave.

If you drive the JCW with less ambition, fun can still be had, and occasionally it can still remind you what made the Cooper such a great car in the first place. However, you could save yourself many thousands of pounds and buy a normal Cooper S, which will do exactly the same, but with the added bonus of not behaving like a naughty puppy the moment you drive it the way its maker intended.

Just as it was in the 1960s, the success of the Cooper brand in the 21st century has been based not just on its cheeky good looks, but also on providing a car that’s genuinely good fun to drive, and good value.

At the £16,000 level there are very few cars of any type that I’d rather drive than a standard Cooper S. The JCW breaks both these rules: at £20,995 it is neither cheap nor anything like as good to drive as its price and specification suggest it should be. Less is often more with cars such as these, and I’d hoped the custodians of the Cooper brand would appreciate that.

Mini Cooper John Cooper Works

ENGINE 1598cc, four cylinders
POWER 211bhp @ 6000rpm
TORQUE192 lb ft @ 1850rpm
TRANSMISSION Six-speed manual
FUEL / CO2 40.9mpg / 165g/km
PERFORMANCE 0-62mph: 6.5sec
TOP SPEED 148mph
PRICE £20,995
ROAD TAX BAND E (£170 for 12 months)
RELEASE DATE Now
VERDICT Good idea, disappoints on road

Worth considering

Volkswagen Scirocco GT £20,940
For Spacious, outstandingly good to drive, well built
Against Looks are not to everyone’s taste

Honda Civic Type-R £18,040
For Great looks, good performance, value for money
Against Poor ride quality, noisy on long journeys