And they weren't disappointed. The scale of the Gallardo's performance, the effectiveness of its four-wheel-drive chassis and the hypnotic draw of its tightly chiselled silhouette are too much for a Ferrari 360 Modena to handle. Job done? Well, not quite. There's another car with such complete dynamics and such mind-altering cross-country pace that it can't be ignored. Since its launch back in 2000, the Porsche 911 Turbo has stood alone as the fastest, most useable, most breathtakingly competent supercar that ΂£100K or so can buy. The Gallardo can only claim to be the ultimate baby supercar if it can stand toe-to-toe with the Turbo on all roads and in all conditions.

To make it really tough for the glamorous Lambo, we're in south Wales. It's raining, freezing- cold and the roads are slick with mushy leaves and mud. We may be a long way from Germany but this is Turbo territory. We've criticised it in the past because it sacrifices some of the 911's delicacy and purity in pursuit of unshakable grip and outrageous speed, but in conditions like these it's crushingly effective. Point-to-point, no car we know is quicker. Imprezas, Evos and the like aren't fit to clean its muddy boots. So the Gallardo has its work cut out. In sunnier climes the Lambo might rely on its traditional supercar strengths to topple the less exotic Porsche, but here it's no-nonsense ability and tactility that will count.

Of course, we mustn't forget that the Gallardo is a Lamborghini unlike any other. For starters it's intended to be useable, exploitable by mere mortals and built to last. Now, these words may well have an Italian equivalent but they've never been in Lamborghini's dictionary until now. Tradition dictates that Sant 'Agata focuses on taking the fight to Ferrari, but you can't help feeling that its new Audi overseers had one eye resolutely fixed on Porsche.

The bald performance figures are spookily similar. The ΂£90,360, 1540kg, 420bhp all-wheel-drive Porsche Turbo gives away nearly 80bhp and carries an extra 20kg, but it's still a mighty thing. Floor the throttle until the twin-turbocharged 3.6-litre flat-six is singing towards 6000rpm, dump the clutch and you'll hit sixty in 4.1sec and the ton in 10 flat. If the straight is long enough, it'll be all done at 189mph. Specify the ΂£8709 Performance Kit (which blesses the Turbo with another 30bhp) and the figures are even more impressive.

The 493bhp 5-litre V10 Gallardo, at 1520kg (and a not inconsiderable ΂£124,600 when fitted with the optional e-gear paddle-shift system), should walk away from the Turbo, but in fact they're remarkably close. We recorded a 0-60 time of 4.4sec in the wet, and though by 100mph the Lambo's ahead, the in-gear times (p92) reveal the Turbo's superior mid-range muscle. Still, 192mph isn't bad for an entry-level model.

Of course, figures tell only a small part of the story. A real supercar makes your heart beat a little faster when you're in its presence, and it should cause you unwittingly to utter absurd, incredulous noises as you pore over every curve and slash. On a wet day in south Wales, a pearlescent yellow Gallardo does the business. I'm following in the Porsche Turbo and all I can say, over-and-over, is... Phwoarrrrr.

But as we shuffle along behind the early-morning traffic I'm reminded why the Porsche Turbo is such an appealing formula. The interior may be fairly ordinary, the view out of the upright screen unremarkable, but it's such a friendly car to just jump in and drive. And I don't just mean drive hard. In traffic it's as docile as a 3-series but with better visibility. The driving position is faultless, the gearbox is light in its action and the immense torque never upsets the drivetrain with the nasty shunts that blight many cars with a top speed approaching 200mph. Unfortunately, Porsche GB couldn't supply a new Turbo for our test, but this kindly-donated, 18-month-old, 18,000-miler feels taut and doesn't so much as rattle even as we turn off the smooth A-roads and hit the kind of bumpy Bs supercars usually hate.

The traffic dissolves, the pace quickens and the 911 starts to show its other great strength: pure, uncut speed. Despite not having the factory power upgrade, the sheer reach of the Turbo defies belief. Pick any gear and it will squeeze you into the seat and keep you there for as long as the revs surge toward the limiter. There's virtually no turbo lag, very little drama, but such an abundance of acceleration that you struggle to keep up with what's unfolding before you. The chassis plays its part here, too. The ride is firm but not GT3-jiggly; the steering lacks the supremely detailed feedback of a rear-driven 911 though it's still terrific, and grip and traction levels are just stupendous. It's a four-wheeled weapon.

The generous owner has allowed one of his friends to bring the car to Wales, a friend who also happens to own a GT3 RS and knows a thing or two about Porsches. Last night he arrived at the hotel with a big grin and a telling conclusion: 'It's so fast, so easy. Anybody could jump in and drive it faster than they've ever been before. Funny, reminded me why I sold my one...' You see, it's this unearthly ability that is both the Turbo's strength and its weakness. It inspires awe but can feel a little clinical. This is where the Gallardo must take the fight to Porsche. If it can match the Turbo's pace and pull on your heartstrings at the same time, it could prove to be irresistible.

After a traffic-clogged run through London the previous morning cursing the Lamborghini's e-gear paddle-shift 'box, trickling over speed humps to preserve that wonderfully aggressive front spoiler and generally feeling both conspicuous and a little foolish, I know that as an everyday proposition the baby Lambo still falls short of the Turbo. I'm sure a manual car would have been a much less stressful partner, but in reality a waist-high, mid-engined car with very little luggage space will never be the perfect commuting tool. Fortunately for the Lambo, there aren't many traffic lights on the Brecon Beacons...

A new day, and I try to wipe the memory of my jerky progress through the London rush hour and start afresh as I approach the glistening Gallardo, parked haphazardly in a muddy layby whilst photographer Gus Gregory turns his attention to the Porsche. Plip the chunky, Audi-derived key, pull the heavy door handle and out swings the door, revealing a cabin that is sober in detail but fantastically dramatic in architecture. You don't need to be a Russian gymnast to get into the hot seat but it's quite a drop down to the firm, narrow-hipped leather chair. The flat-bottomed steering wheel is perfectly placed and adjustable for both reach and rake, the paddles within easy reach. The huge windscreen affords a wonderful view ahead but the sweeping A-pillars cut into your peripheral vision and the shallow side windows hem you in a little. The Gallardo instantly feels big and a little intimidating.

Turn the key and the starter motor whirs frantically for a good couple of seconds before the V10 catches. It's a noise to die for: deep and mellow at idle yet instantly ramping up into a resonant offbeat bark with just a tickle of the throttle. It's a very different noise to the legendary Lamborghini V12, less busy and, despite knocking out 99bhp per litre, somehow less strained. Go for the brake and you'll instinctively hit the loud pedal - the translation from left- to right-hand drive has resulted in quite an offset pedal arrangement. Readjust, flick the right-hand paddle whilst simultaneously prodding the 'Sport' button on the centre console with your left hand (well, you have to) and you're smoothly away.

The e-gear system works well enough when you're pulling away swiftly, but throw in an armful of steering lock or the need to creep off the line, and it gets horribly jerky and inconsistent. On full lock the diffs seem to tie themselves in knots, too, so any getaway is a farce of kangarooing and nasty graunches from the transmission. Fortunately, once up to speed it's altogether better. Changes are lightning quick and much smoother than the equivalent Ferrari system despite utilising similar Magnetti Marelli software. If Lamborghini can perfect the subtleties of gentle manoeuvring, e-gear will be almost as good as that new-fangled invention, the manual gearbox...

Transmission gripes aside, the Gallardo rapidly worms its way into my affections. That engine is a masterstroke, endowing the Lambo with instant and crushing shove but, just as crucially, the true supercar spirit. Ferrari has always distinguished its smaller mid-engined road cars from the V12 big-hitters with zingy rev-hungry motors, but the Gallardo's torque-swollen V10 offers a more authentic flavour of the fearsome breed that has proudly trickled out of Italy for decades. The tight-fisted damping, slightly reluctant turn-in and the weightiness of the steering also seem to be a nod to traditional supercar qualities.

The gearing is real supercar stuff; second is good for 85mph, third will take you to over 110mph - but such is the torque of the V10 that you naturally seem to pull for another gear at 6500rpm or so, 1500rpm shy of the redline. Even just scratching the surface of the engine's terrific range sees the Gallardo make blistering progress. Up the ante and it's clear the Turbo will need to dig deep within its armoury of grip, agility and power to see off the Lambo. It takes real commitment to wring out the Lambo to the full 8000rpm, such is the rate of acceleration as the needle arcs towards the danger zone. Previous Gallardos we've driven have had a totally linear delivery, but this V10 kicks at just under 4000rpm and again at around 7000rpm and is all the more enjoyable for it.

With 30 per cent of drive being sent to the front wheels in steady-state driving and up to 50 per cent when you're asking serious questions of the gumball Pirellis, the Gallardo is never found wanting for traction. Turn-in is a little hesitant, but then the front stays faithful even when you get hard on the power. The Gallardo can be induced to slide at the rear just a little on the exit from medium-speed corners, but watch it on greasy hairpins or the torque will send you sideways quicker than the traction control can react.

If only the steering had a little more feel. Initially it feels spot-on in terms of weight and feel, but somewhere around six-tenths it all goes a bit vague. On fast sweepers that you can attack with total conviction in the Porsche, the Gallardo creates an element of doubt. The grip is there but it's a bit of a leap of faith. Even so, the Gallardo is essentially viceless. Understeer is the first sign that you're beginning to reach the outer edge of its abilities; stay on the power and it will tighten its line gradually. Total commitment can bring a few degrees of power oversteer but it's not something you feel inclined to indulge in very often, as the speed required is just too great.

The Turbo is an enigma. Drive it back-to-back with anything from a Carrera to a GT3 and it feels a bit lifeless. Effective, certainly, but it doesn't engage. However, in isolation it's utterly superb. And the Gallardo has to give best to the Turbo in two critical areas. Steering feel is one, communication through the brake pedal the other. Combined, these two faults amount to a significant problem for the Lambo on very tight, bumpy and unsighted roads. Conversely, the Porsche grows in stature as the road becomes more challenging; shrugging off surface changes, murdering braking areas and firing out of corners with all four tyres ripping chunks out of the tarmac. Perhaps most galling for the Lambo is that the Turbo feels considerably faster in these situations. Its shorter gearing and huge torque (413lb ft all the way from 2700rpm to 4600rpm) seem to speed the passage of time itself.

This isn't quite going to plan for the Lambo. I'd expected the Turbo to feel anaesthetised and aloof, but from the gently writhing steering wheel to the deliciously malleable handling balance, it's the 911 that feels more organic. It squats hard out of tight corners, goes light at the front over crests and demands a bit of a lift to commit the front tyres and bring the rear weight bias into play the quicker you drive. On these narrow, punishing roads the Lambo is still scary fast, but slightly leaden in comparison.

Photography finished, we head towards a road that should be more to the Gallardo's liking. It's fast, undulating, well-sighted and totally empty. The surface is broken in parts and worn smooth in others and there's still a sheen of water to contend with. This is supercar country and the Gallardo needs to come alive. I take the Porsche for a long run first, to set the benchmark. It hammers up the straights, flows with real grace through the fast sweepers. There are a couple of tight corners hidden by lofty crests, but the Porsche refuses to be wrong-footed. And then it hits me that it's doing that old Turbo thing: I'm just along for the ride; the 911 is operating in its own dimension.

Our GT3 RS-owning friend is behind in the Gallardo, going just as hard. He has his doubts about the Gallardo, too, after being left slightly cold by it on this morning's photography route. But judging by the look on his face, the Lambo might just have revealed something more of itself. We turn around and I follow his lead. The Gallardo's deep warble drowns out the muted flat-six of the Turbo, but corner for corner they're pretty evenly matched. The Lambo's power advantage only begins to tell when the speeds rise deep into licence-losing territory and that long gearing starts to make some sense.

It looks totally stable through both slow and fast corners, there's no discernible roll at all, and despite the low ride height the damping keeps the nose proud of the unpredictable surface. Pulling back into our parking spot, I'm excited about the Gallardo again. Now I want to experience what it does on this road for myself.

What it does is peel back some of the layers of insulation that blighted it on the awkward, stop-start road we'd driven earlier in the day. The brake pedal is still mushy (but at least it's consistently mushy and resistant to fade), the steering still not the last word in communication, but the chassis and engine are so good that any niggles are banished to the background. The Gallardo really rides the bumps well, allowing you to take that leap of faith with the front end and discover just how much grip is on offer. The rewards redouble with every ounce of commitment you throw at it, and the Gallardo lunges at the horizon with a fanatic's fearless zeal. Finally, it stamps its mark on this test and elevates itself above the freakishly competent Porsche.

Lamborghini and Audi have trodden a very fine line with the Gallardo. It retains the outrageous genes of past glories through its gorgeous styling and charismatic engine, but marries them to the kind of ruthless efficiency that makes the 911 Turbo such a formidable yet practical road car. It hopes to exploit the middle ground between Ferrari 360 and Porsche Turbo, which seems a sensible game plan. For many this will be too calculating a premise to spawn a real Lamborghini. Yet, after two days and many hundreds of miles in its company, the Gallardo still felt like an event whenever that all-alloy V10 burst into life. The Lamborghini DNA is there to see, and to hear. It's a triumph.

On the long slog back home it had one more duty to fulfil. In the pitch dark and pouring rain I nosed the Gallardo onto Millbrook Proving Ground's mile straight, selected Sport, flicked off the ESP and stamped on the throttle. Revs flared, all four wheels struggled for grip and then the speed just piled on and on. In truly atrocious conditions it hit 60mph in 4.4sec, 100mph flashed by in 9.7sec and 150mph in 23.3sec. The 911 Turbo couldn't match that - not even in the dry. King of the all-weather supercars? I'll give you a clue: it's made in Italy.