David Finlay just knows that Mercedes is the only one for him.

The second question is the most common you are ever asked, and the hardest to answer. Your reply to the first has established that you are a motoring journalist, whereupon you brace yourself...yes, here it comes: ''So if you could buy any car at all, which one would it be?''

For a very long time I had no answer to this. Then I drove a Mercedes C36 AMG, and that settled the matter. To an extent matched by at the most two other cars since, the C36 was to all intents and purposes the very dab.

C36s would have had to stay in production for centuries before I could have afforded one, and in fact they're not in production now. But race team and tuning concern AMG is still, with official backing, turning out amazing modified versions of Mercedes products.

The two most recently launched are the C43 and the E55. The names tell you that these are C-Class and E-Class variants with 4.3 and 5.5-litre engines. The fact that they are among the most extraordinary cars you can buy is something you have to discover for yourself.

The E55, which I drove first, was the first car in years to inspire awe in me. With a maximum power output, if you must know, of 354bhp, but more importantly with useful power available all the time, it is very fast indeed, and up to a point it handles exceptionally well. ESP (Electronic Stability Program) stops slides before they start, and the brakes are heart-stoppingly powerful, though you still have to drive with a lot of care, simply because if you don't the numbers will stop adding up in your favour. The modified suspension deals smartly with minor bumps, but the overall ride is still luxury-cruiser style. Which is appropriate enough, because for all its performance that's what the E55 really is. If you try to push it harder than it wants to go it becomes disappointingly clumsy, so relax and let the car do the work.

The C43, next in line to my darling C36, is altogether different. It's less powerful (306bhp) than the E55, with neither the acceleration nor brakes at the same level.

What a driving experience, though. Leave a parking space and it's already telling you enticing stories through the firm steering and the more purposefully tuned suspension (still a comfortable ride nevertheless).

Put the foot down and it roars, at 1990s-acceptable decibels but with as much character as you could wish for. Take it over bumps, round sweeping bends, through difficult corner combinations, and it never loses its poise.

I loved it. But the best bit came after all that, when I drove the last 10 miles to base camp so slowly that if traffic had been heavier I would have had caravanners looking impatiently for a way past.

The C43 behaved as artfully in this situation as it had when it was being pushed along, and I felt entirely at peace with it. It became my new answer to that old ''favourite car'' question.

The C43 costs #47,640, the E55 #60,540, and there are estate versions at #49,070 and #62,840.

Assuming finance isn't an issue, the choice comes down to personality. If you love the art of building cars, buy an E55. If you love the art of driving them, the C43 is for you.