But boy, what a choice career ladder-climbers have got – there's a new Jaguar XJ for the traditionalists, the BMW 7-series for those who won't forsake driving enjoyment and the evergreen Mercedes-Benz S-class for drivers who want the ultimate status symbol on their sweeping gravelled driveways.

But if I was in that position, my eyes would be poring over the brochure for Audi's A8 – an aluminium-bodied, four-wheel drive technological showcase wrapped up in the discreet styling which has become synonymous with the marque from Ingolstadt. Until recently there was a choice of two A8s, both with petrol engines in either 3.7 or 4.2-litre guises. But now there is a third, and potentially most interesting, model – the 4.0-litre diesel.

Running the same quattro running gear as its petrol siblings, the 4.0 TDI shoehorns a twin-turbocharged V8 diesel engine under its elegant bonnet, offering 273bhp and a massive 480lb-ft of torque.

With that much torque on offer, the A8 TDI has colossal mid-range performance which puts the petrol-powered A8s to shame.

Pick any speed on any type of road, floor the throttle and within seconds you will have disappeared into the distance at an alarming rate.

I know it's a cliche but this really is sledgehammer performance, only interrupted by the low red line which is common to all diesel engines.

And with its four-wheel drive system, you can push the A8 into corners with far more confidence than you would in its rivals which all run the traditional rear-wheel drive layout.

Riding on big, fat alloy wheels and low profile tyres, the A8 feels so planted on the road that no matter what weather conditions are prevailing, you can access all the A8's performance without fear of sliding off the road. But while the A8 is incredibly composed on the open road, in town it reveals a darker side.

Sitting at traffic lights, the big diesel lump up front throbs away and sends vibrations through the cabin – not what you would expect from a luxury saloon costing nearly £60,000.

And the fuel economy benefits aren't much to write home about either – the TDI model returns an average of 28.8mpg, compared with 23.7mpg and 23.5mpg for the 3.7 and 4.2 models. But then again, at this level the difference of a few miles per gallon isn't going to break the bank, is it?

And neither is the fact that the TDI is the most expensive in the range, costing £57,560 – £6,690 more than the A8 3.7 and £2,760 more than the 4.2 model. And if you're looking to lower your benefit-in-kind tax bill by opting for a diesel, think again. Even though the diesel has lower emissions than the petrol versions, it still falls into the maximum 35% company car tax band.

With its higher front-end price, it will actually cost drivers more in tax – £670 a month for a 40% tax-payer, compared to £639 for the 4.2-litre and £593 for the 3.7-litre.

So financially, drivers will be better off in one of the petrol models, but I would still go for the diesel and hang the cost. It's blistering performance more than makes up for its lack of refinement around town.

But I may defer that decision as next year a more cost-effective 3.0-litre diesel A8 arrives to compete head-on with the Mercedes-Benz S320 CDI and BMW 730d.

Model: Audi A8 4.0 TDI Quattro
Engine (cc): 3,936
Power (bhp/rpm): 273/3,750
Torque (lb-ft/rpm): 480/1,800
Max speed (mph): 155 (limited)
0-60mph (secs): 6.7
Fuel consumption (mpg): 29.4
CO2 emissions (g/km): 265
Price (OTR): £57,560