Without a doubt, the Alfa Romeo 4C is the most important Alfa Romeo for decades.

Alfa has spent many years being messed about by successive managements, every one with different half-cooked ideas, then quite a few more. Recently it has had its better-known values attached to B and C-segment hatchbacks - the Mito and Giulietta - because that is where the money is.

Editor-in-chief
Give me a track to play on, and I'd choose a 4C over any Ferrari

Yet no car in recent history has deliberately set out to embody Alfa values. The 8C Competizione helped, of course, but it was really only a concept made good.

In truth, it is at least 30 years since Alfa Romeo has built a car for real people that directly and affordably expresses its values. This is the 4C's mission and it is why it is so very significant.

Nothing about the fixed-head, two-seat 4C better underscores its seriousness than the fact that its chassis is an extremely rigid carbonfibre tub weighing just 65kg. This featherweight foundation, plus Alfa's use of a new, 22kg lighter, all-aluminium, direct-injection four-cylinder 1750 turbo engine - and a myriad more weight-saving features - mean that, parked in the street ready to go, a 4C weighs just 925kg. That's about the same as a Lotus Exige.

Given that the engine produces 240bhp at 6000rpm, plus 258lb ft of torque between 2100rpm and 4000rpm, its power-to-weight ratio of 259bhp per tonne is really something to crow about, matching that of many big-capacity supercars at more than twice the price and power.

Small wonder that the Alfa Romeo 4C can top 155mph and sprint 0-62mph in just 4.5sec, while returning an impressive 41.5mpg on the combined cycle. As our figures show, a basic Porsche Cayman costs a bit less and goes a bit faster, but doesn't accelerate as quickly and uses more fuel doing it.

More notably the carbon tub puts the 4C on a level - in chassis terms - with the likes of McLaren and Ferrari, yet the 4C will set you back just £45,000 when supplies start to flow at a rate of 3500 units a year before the year-end. Don't get your hopes up, mind. Only 1000 cars a year are earmarked for Europe, and about 200 of those for the UK. All 500 examples of the all-white launch edition have sold out already, and Britain's allocation of regular models for 2014 also all have names against them. 

Still, if you can't buy yourself a 4C for a while, you can at least admire its specification. It is a very compact coupé with a transverse mid-engine layout, carrying 60 per cent of its weight over its driven rear wheels. It has a standard six-speed dual-clutch automatic gearbox with paddle shifters. The all-disc brakes are by Brembo; the discs are specially coated to improve both initial bite and feel.

The unique shape, created at Alfa's Turin-based Centro Stile, has been refined over many hours in the wind tunnel so that it has both negative lift at speed and a Cd of 0.35, a low figure considering downforce creates drag. Oh yes, and the steering is entirely unassisted, and its gearing is high enough to let you take 90 per cent of corners without shifting your hands from the wheel.

When you meet your first 4C, your impression of it goes through several phases on its way to a confirmed opinion. At first you think Lotus Exige, because it's diminutive (just four metres long), has a transverse four-cylinder engine, carries a great name on the nose and its price is in the Exige ballpark.

Then you'll notice a relationship in its haunch and rear air scoop shapes to a Ferrari F12. There's Lancia Stratos in it, too; check those side-window shapes, the semicircular windscreen base and the positioning of the screen pillars (and door hinges), unusually far back in the car. And all the time you're seeing echoes of the 8C Competizione, so influential on all modern Alfas. 

Afterwards, someone starts the engine for the first time and drives the 4C up the road. You hear that potent exhaust bark (who says legal exhausts can't still inspire?) and the dramatic wastegate chirrup and chatter as the ignition cuts at the first gearchange.

That part is reminiscent of a current 1.6-litre rally car, also turbocharged, small-engined and very potent. Spend a day with the 4C as we did and you'll end up deciding it's an individual that draws influence from whatever's good, especially if its Italian, without owing too much to anyone.

More surprises inside. The driver's door opens to reveal a considerably higher sill than most cars, although not as obstructive as a Lotus Exige's, and made of carbonfibre, not extruded aluminium.

Put your leading foot as far down the footwell as you can, slide your backside down the well bolstered semi-race bucket seat (ours faced with pleasing Alcantara) and pull your second leg in around the door hinge, too far back for easy access but sensible in every other way. First thing you'll notice is lots of naked carbonfibre: that's the tub, undisguised.

The second is the simple, almost competition car aura of the interior: matt black everywhere and hard plastic on the dash, yet right for this car, from which driving purists can delete the air con and audio. The doors have simple leather pull-handles reminiscent of those in revered, stripped-out Porsche 911s of yore, and the floor covering is durable, not luxurious. This may not be quite what you were expecting, but its right for a car whose big objective is low weight.

There are wallet-like slots under the dash and between the seats for carrying things (plus a couple of the inevitable cup-holders safely out of view under your elbow) but this cabin is built for simplicity, not convenience.

A TFT screen ahead carries a large electronic tacho dial surrounded by essential info (speed, gear position, temp, fuel and - incongruously - day and date). This whole display changes shape and colour when you select the new-for-4C ‘Race’ position on the familiar DNA quadrant on the low centre console that lets you you configure throttle response, gearchange time and degree of chassis stability intrusion from four settings.

All you need do to start the engine is to put your foot on the brake (there are only two pedals, remember, plus an alloy-faced rest for your redundant clutch foot) and twist the key.

No hunting around the cockpit for starter buttons or posting plastic bricks into slots. Twist, and with no ceremony, no dashboard messages and no crowd-pleasing blip, the 4C's engine fires promptly and settles immediately into a typically four-cylinder idle. In a way, it's a bit shocking. There seems little soundproofing to speak of: you can hear the valve gear rustling away at close quarters in a way most manufacturers wouldn't allow.

But why not? This is a brand new Alfa engine, after all, and on a horsepower/litre basis it roundly beats some of the greatest race engines ever built. Blip the engine and it barks instantly and gruffly, as if fed by a pair of double Webers. Sounds like fun.

Reach down on to the abbreviated centre console and select the '1' button. That hooks up first gear and dictates that you'll need to change gears yourself via paddles. You could have chosen 'A/M' but that would have been self-shift mode. Apply a little throttle and the car moves off instantly, like an Elise or an Atom. Here's how you can know instantly, without the assistance of a weighbridge, that the Alfa Romeo 4C is a light car.

First is noisy and short, but the thrust is mighty. You need to be respectably quick on the right paddle because you'll close fast on the 6500rpm redline. The following gearchange itself is quick and smooth, mechanically speaking, and speeds up 30 per cent in Dynamic or Race, but the way the clutch system matches revs with speed is always exemplary. If you're expecting instantaneous, Ferrari-style controlled explosions as the cogs swap, you're not going to get them.

Performance and flexibility are this powertrain's forte. The exhaust note can be raucous and the combined racket of ignition-cut and wastegate whoop when you change gear is never peaceful, always inspiring. From outside, the car sounds amazing.

From inside, the quality's not quite the same, though it would always entertain me. Used to the full, the car feels properly quick, especially between 60 and 100mph where it seems to gain pace as rapidly as much bigger cars but without their big-cube effort. The engine's thrust doesn't grow beyond 5500rpm with quite the top-end shove you expect, but the truth is that in Dynamic or Race, using plenty of throttle and changing at 5500rpm, you'll be among the fastest cars on road or track.

Passing manoeuvres are special fun, because the car is compact and gains speed with so little effort. So is slingshotting out of slow bends: there's strong urge from 2000rpm which means almost any gear will do. And the noise is always great.

In countries like the UK, the 4C might seem a mite overgeared; it does close to 30mph per 1000rpm in top. Fortunately, it has the torque to carry it, and you can understand why Alfa has gone down that route; the car would be more frantic with ratios closed up by lower overall gearing.

Inevitably, Alfa has had some complaints about both its choice of a DCT gearbox (why not a stick shift?) and a small-capacity turbo four-cylinder engine (why not a creamy V6?) but the car's performance answers both of these pretty convincingly.

The 1750 engine delivers a unique form of sound and thrust consistent with its lightweight targets. The DCT, as many a manufacturer knows, is the 'box that 90 per cent of owners would choose if it offered both; why spend millions engineering something that few will buy?

Thanks to the lightness, the wide track, the chassis rigidity, the low centre of gravity and lack of overhangs - plus all-independent suspension and the fact that a bunch of hard-driving Italian engineers have given it death in places like Alfa’s famous Balocco test track - the 4C’s roadholding and ride quality are just brilliant. The car will understeer a little near the limit, but getting it to oversteer is a helluva job.

We tried repeatedly, and were rewarded, once for a second, with a brief and reluctant tail wag. Meanwhile, the car rides with a Lotus-like serenity and composure: firm but amazingly flat and perfectly damped. Comfort is likely to be impressive even on gnarly UK roads. 

This is one of those cars that doesn't need huge rubber hoops to deliver grip, although our test car was admittedly on the optional tyre pack, 205/40 ZR18s in front and 235/35 ZR19s on the back. The standard wheels are 17in front, 18in rear. On whichever, this light car and its fancy Brembo brakes can stop from 100km/h in just 35 metres, a performance that eludes any heavy supercar.

The unassisted steering takes some getting used to, but becomes one of the 4C's principal virtues. At standstill, you have to re-learn the experience of supplying muscle; it feels weird. But at 2mph and all speed thereafter it's fine. It loads more than power-assist systems as cornering speeds rise, but you feel much more of the road.

At sane speeds (under 100mph) it's superbly stable. Above that, you have to remember - again, as you used to in the unassisted breed of early Porsche 911 - not to chase small steering corrections. The car simply ‘walks’ a little on uneven surfaces, taken very fast. Let it want, and it'll track like an arrow.

This 4C is an excellent driver's car, although it won't suit everyone. It has a few flaws. Some will say a Porsche Cayman is more ‘grown-up’ and ‘finished’, and they are right. It is certainly more of a car that you could easily drive to work.

But, put frankly, two hundred Britons a year will not care a damn. They will not be thinking about Porsches. They will be Alfa 4C owners, and they will have discovered one of those cars - and at only £45,000 - that truly stands apart from the rest.