IF environmental concerns mean that one day in the future we all have to drive tiny city cars, then let's hope that little gems like the SEAT Mii are still available.

Usually, owning a car of this size means making a few compromises.

For every advantage you gain - such as price and economy - you have to accept there will be disadvantages like weedy performance and lack of interior space.

But the Mii is a surprisingly complete package that leaves you facing only one real downside - a lack of room in the boot.

The Mii is the sister car to the Volkswagen up! and the Skoda Citigo, and while none of them will win any beauty contests, the SEAT is probably the best-looking of the three.

They're all a bit boxy but the Mii has a more dynamically-styled front and looks more sporty than the other two.

By contrast, the Skoda looks a bit anonymous and the  VW has the face of an over-eager puppy - which may appeal to some, of course.

The biggest surprise you'll have when you drive a Mii is its performance.

For its size, the engine is remarkable. Look only at the figures, and  - apart from the fuel economy - you'll be unimpressed: 3 cylinders, 999cc, max power 60PS, top speed 99mph and a 0-62mph time of just over 14 seconds all sound a bit dull.

But on the road, it's a different story - the engine feels lively and full of beans and if you use the gears to full effect you won't find yourself embarrassed at the traffic lights.

Even on the motorway, where city cars usually fear to tread, there is no need to sit at 50mph behind slow-moving wagons in the inside lane. Providing you plan your overtaking properly, there is still plenty of acceleration to be had even when travelling at the legal limit.

Bear in mind that we tested the 60PS version - there is also a more expensive 75PS option which is that little bit quicker.

Naturally, a car of this size and low weight will always feel more at home in the city, and it does get blown about a bit by the slipstream of lorries and coaches on faster roads.

But I completed a 300-mile motorway trip in the car quite comfortably.

The three-cylinder layout is a little noisy at lower speeds - it sometimes sounds like the exhaust is blowing - but this becomes smoother and quieter at higher revs.

The engine's big bonus is its economy. SEAT's claimed 62mpg for combined city/country driving is achievable, although I struggled to match the 72mpg claimed for ‘extra urban' motoring. To be fair, around town I managed slightly better then the claimed 50mpg, a more important result for the car considering its usual environment.

The ride is excellent, although the narrow track means speed bumps have to be negotiated with care.

The steering has a nice weight to it on the road, but is light enough for easy parking. It goes without saying that parking is a doddle in such a small car and you don't really need the optional parking sensor (part of a £530 pack including trip computer, front fog lamps and a fairly pointless cruise control).

One extra that is worth the money is the SEAT Portable System. For £275, you get a handy little sat nav unit that plugs into a stalk that fits into a socket on the top of the dash. It causes no unsightly sucker marks on the windscreen and fits neatly into the glovebox when parked.

Unlike a normal portable unit, it integrates with the car's audio systems, allowing you to control radio, CD and some auxiliary devices from its touchscreen. It also offers enhanced trip computer functions as well.

Also worth ticking on the options list is the £200 Safety Assist, which applies the brakes if it senses an imminent frontal collision at city speeds.

Inside, the interior seems basic at first but while there is plenty of untrimmed metal on view, the door handles and panels are stylish and pleasant to touch and use.

It's actually a roomy little car, particularly in five-door form as I tried, and the panoramic sunroof fitted to the car (a £660 option) added to the feeling  of space.

I was particularly impressed with the ease of fitting child seats in the back - it's a pet hate of mine that in many, much larger cars, the seat belt buckle often disappears beneath the base of the child seat. This makes it almost impossible for a smaller child to fasten his or her own belt and ends up with the harassed parent having to lean in from the kerb and pull the seat out in order to clunk and/or click.

No such problem in the Mii - there is a couple of inches to spare either side of the seat base and ISOFIX points are fitted as standard.

My only criticism is that the boot, while reasonably deep, is quite small and would struggle to accommodate a family's weekly supermarket shop. The rear seats will split and fold down to create more space, but obviously not if they are occupied.

A bit more room for storage and this would be an even more impressive little car.