Audi A8 4.2 TDI SE

The huge peak is produced very low in the rev range and for longer than its 4.0-litre predecessor - from 1,600rpm up to 3,500rpm. This makes the amazing acceleration even more accessible.

Combined with extra power - up from 275bhp to 321bhp - a weight drop of 15kg and a new six-speed automatic gearbox, the results are sensational. The 0-60mph time is cut from 6.7 to 5.9 seconds, but it's the deep-chested thrust available at any speed and in any gear that impresses most.

Refinement is also superb, with little more than a smooth V8 rumble to be heard. The 29.4mpg combined economy figure is an improvement on that offered by the outgoing diesel, and gives the car the potential to travel in excess of 600 miles on a single tank. Carbon dioxide emissions are down 7g/km, although at 258g/km the new A8 is still in the top 35 per cent company tax band.

Downsides? The gearbox is jerky, and most buyers will be more than happy with the 3.0 TDI, which costs ΂£48,365 as opposed to ΂£58,605 for the 4.2-litre. Still, that's the same as Audi charged for the old 4.0 TDI, a car the newcomer betters in every area.