BMW UK's then managing director stood with his back to me, staring out of his office window, hands clenched behind his back (a pose he often seemed to adopt when talking to people). "BMW will never," he said, with Churchillian intonations, "go beyond a 1% share of the UK market. It would remove our exclusivity and appeal."Well that was then, and this is now, with BMW currently on 4.45% of the UK market, and MINI adding another 1.84%. Exclusivity? They're everywhere! And yet the 3-Series on the face of it the German equivalent of a Mondeo - continues to exert an almost magical hold on British buyers.A few days swanning around in the latest 330d M Sport saloon served merely to ram that message home. Here I must declare an interest I own and run a 323i SE, so I suppose I'm biased. Not so biased, though, that I can't prefer the shape of my car to the angular and to my eye rather ungainly lines of the current 3-Series crop.This car admittedly looked impressive with its 18" light alloys and ultra low-profile run-flat tyres virtually filling the wheelarches. But what you gain in looks, stance and street cred you lose in road noise and reaction to surface imperfections, exacerbated by the M Sport's suspension tweaks. Personally I cannot believe it's quicker across country and through the bends than standard, but boys will be boys and they must have their flash wheels and tyres.The overall attributes of the 3-Series are too well known to bear repetition here. The heart of this car is the superb three-litre power unit common to both SE and M Sport models. You can guess just - that it's a diesel on start-up, largely from the idle speed, but the harsh clatter and knock of a cold diesel has been almost completely suppressed. And once on the move I would defy anyone to tell the fuel employed.That it develops 231bhp is impressive enough - it's the most powerful diesel ever to be fitted to a 3-Series - but it's the stonking torque that defines the car's performance. 500Nm (369lb/ft) in a virtually flat line from 1750rpm to 3000rpm means you can almost feel the car wanting to revolve around its own crankshaft as you open the throttle; such is the surge of acceleration. Given so much torque a six-speed box (short gearlever in the M Sport) seems superfluous - seamless power is available in any gear at almost any speed.A few short years ago the idea of a diesel BMW would be unthinkable, let alone one which could sprint from 0-62 in 6.7 seconds and surge on up to an electronically limited maximum of 155mph. But given that you can enjoy that level of performance allied to a combined official fuel consumption figure approaching 45mpg, you wonder why anyone would choose petrol.So what does the M Sport label buy you? Apart from an eye-watering price tag, plus on the test car two grand worth of "professional" satnav, almost a grand each of leather seats and electric seat controls, and £500 worth of Bluetooth phone prep, the famous appendage gets you: those wheels and tyres, brushed aluminium interior trim, a body kit, sill trims, an M Sport steering wheel, and sports seats which I found too tight below the shoulders - and I'm by no means a big person.As you've probably guessed by now, I was enormously impressed by the car and in particular the engine, but if it were my choice I'd forgo the M Sport fripperies. In fact I think the marketeers at Bracknell need to be cautious to avoid over-use of this M Sport tag it's in danger of diminishing the legendary qualities of the proper "M" cars.This was an immensely capable car, holding its own with some of the best performance machinery around, yet delivering fuel consumption figures to help ease your conscience over global warming and conservation of resources as well as providing prodigious range.But allow me one last Grumpy Old Man rant. Am I alone in hating the iDrive control knob? I'm told car hire companies are anxious about American and Japanese businessmen at airports spending upwards of 20 minutes trying to work its functions out. I had to dig out the manual to find out how to change the pre-set stations on the radio. Oh, and the manual is now so bulky it won't fit in the glove box, and you have to get out and go to the boot to retrieve it. Progress? Harrumph! Engine 2993 cc, 6 cylinders Power 231 bhp @4000 rpm Torque 369 ib/ft @1750 rpm Transmission 6 speed manual Fuel/CO2 43.5 mpg / 174 g/km Acceleration 0-62mph: 6.7sec Top speed 155 mph Price From £32706.00 approx Release date 12/09/2005