We've tested several other Ibizas at CARkeys, and you can read about them elsewhere. But this one is a bit different.First of all, it's one of the most astonishing hot hatchbacks I've ever driven. Second, it's a diesel. While these two facts would have been irreconcilable a decade ago, they make perfect sense nowadays - diesel technology has been marching forward at such a rate that, as we have seen, it's even possible to go racing in a diesel van with some optimism of success.The 1.9-litre unit fitted to this Ibiza produces 128bhp. That would be a handsome power output for the car if a petrol engine were doing the work, but since this is a diesel you know that there must be an absolutely phenomenal amount of mid-range urge.And indeed there is. I'll describe the effects in a moment, but first let's play with some numbers. The Ibiza uses a six-speed gearbox, and the ratios are by no stretch of the imagination close. In top gear, you get 39mph per 1000rpm, which means you can cruise along a motorway at not much more than tickover speed. It should also mean that any attempt to accelerate in this gear will rattle the paint off the doors. Not in this case.There is hardly any other car on the market that can sensibly cope with this sort of gearing. The Ibiza handles it easily. It will accelerate strongly, or climb reasonably steep hills, without any suggestion that it would prefer you to drop down a ratio or two.In the lower gears the performance is incredible. If you floor the accelerator below 1600rpm, nothing much happens at first, but once you hit that magic figure the Ibiza simply takes off. There is so much torque for a car of this size (168lb/ft at 1900rpm) that you can swish along country roads in genuine hot-hatch style without ever allowing the engine to exceed 2500rpm. And if you really want to go quickly, you can let it run up to the dizzy heights of 4000rpm before the power starts to fall off.It's so quick, in fact, that despite the Sport badge there is a suspicion that SEAT hasn't done quite enough work on the brakes or suspension. Oh, the Ibiza stops well enough, and handles reasonably, but neither of these two areas match the straightline performance. It's quite easy to overdo things even on a short straight and leave yourself with a lot to sort out before the next corner.With slightly stiffer suspension and larger brakes, this would be just about the best - and certainly most surprising - hot hatch on the market. Even now, it is in its own way perhaps the most remarkable performance-oriented road car we've ever tested.Second opinion: If the Ibiza 1.9 TDi Sport was a small boy "he" would have holes in "his" knees and elbows and scuff marks all round "his" shoes. This car has "hooligan" stamped all the way through it. Ignore the unassuming, shiny exterior and drab black interior, hit the loud pedal and watch your grin expand beyond the confines of the rear view mirror. The 128bhp figure doesn't do the car justice either, but the torque does. This is a very quick wee tyke, but that is also its problem. It's too quick for the suspension and the brakes, and that could easily lead to holes in its bumpers and scuff marks around the wheelarches. The car is quicker than it looks and fun to drive, but requires a clip around the earholes when tackling sharp bends and sudden stops. John Fife. Engine 1896cc, 4 cylinders Power 128bhp Transmission 6-speed manual Fuel/CO2 55.4mpg / 138g/km Acceleration 0-62mph: 9.4 seconds Top speed 129mph Price £13,495 Release date 15/05/2010