I wouldn't like to have much more power in such a short-wheelbase, basically city car as the Lupo GTi, and I don't see that Volkswagen could have made it significantly lighter without using super-expensive materials or throwing out the back seats and all the trim. So the power-to-weight ratio of this little bombshell is OK by me.Bombshell - city car - is there a split personality here, or are we going completely overboard in describing this machine? Yes and no, in that order. The GTi has the same tiny overall dimensions as the economy versions, but the 1.6-litre 16-valve engine is tuned to 125bhp, and the weight is pared down thanks to the use of aluminium for the bonnet, doors and wheelarches.The idea of a really quick version of Volkswagen's smallest hatchback seems bizarre, unless you realise that this is the road-going version of the Lupo Cup cars as raced in the one-model ADAC series in Germany.There are lots of external differences from the lesser Lupos, including a deeper front bumper with large air inlets, a mesh grille, 15" Bathurst alloy wheels in wider than standard arches, a rear roof spoiler and a pair of mean-looking tailpipes.Inside, you get sports front seats, alloy pedals, a leather-rimmed steering wheel, chrome-rimmed instruments and various other sporty odds and ends. Although the GTi certainly isn't cheap in standard trim, leather upholstery is a worthwhile extra-cost option. Satellite navigation at extra cost again? I wouldn't bother, myself.With a car like this, you want plenty of gears and very strong brakes. The GTi comes as standard with a well-stacked six-speed box, plus ABS, EBD and discs all round, ventilated at the front.Having so little weight to haul around, it will rocket off from a standing start, wheelspinning if you overdo the loud pedal, and elbowing in a bout of torque steer just to keep your mind on the business.Like almost all short-wheelbase cars with maximum power for their size, it will dart around, especially on bumpy surfaces, unless you (a) keep a firm grip on things, or (b) don't floor the throttle all the time.The snag is, the Lupo GTi is such a blast that it's difficult to pay much attention to (b). This car will dart along minor roads in a most exhilarating fashion, small enough to take an elbows-in line to tight corners, and yet with enough throttle response to fire exuberantly along the straights.Thanks to the six-speed transmission, the GTi doesn't roar its head off at motorway speeds. An indicated 70mph comes up at 3200rpm.Like all versions of the Lupo/Arosa design, the GTi feels quite spacious in the front seat area, but an over-the-shoulder glance - showing the rear screen so close - makes it clear that there's very little rear-seat space, and minimal luggage room. But since the standard Lupos you see on the road don't do much heavy passenger or luggage hauling, and the GTi is actually something like a roofed sports car, none of that seems to matter.The GTi is well built and well finished, and the more you examine it, the less crazy the £12,980 showroom price seems. As well as the aluminium panels, the six-speed box and the powerful brakes, standard equipment includes power steering, a height-adjustable steering wheel, xenon headlamps and electric windows.I don't know if there's a price tag on the fun element, but it's there too, most decidedly. Engine 1598cc, 4 cylinders Power 125bhp Transmission 6-speed manual Fuel/CO2 38.2mpg / 178g/km Acceleration 0-62mph: 8.3 seconds Top speed 127mph Price £12,980 Details correct at publication date