Hamish McRae: Engineering alone cannot create sweetness and light

The basic concept has to be right but the detail makes the difference

What makes a car really sweet? There are some cars that just fit together very well. It is not just a question of build quality, though that matters hugely. Nor is it just good engineering, though without that they will soon disappear. Nor is it even looking pretty -- indeed there are some pug-ugly cars that are sufficiently together to inspire delight, the VW Beetle and the Citroën 2CV being prime examples.

It certainly has nothing to do with size or cost, for there are small, cheap cars that thrill (the original Mini) and big, expensive ones that disappoint (the early 1990s S-Class Mercedes -- the one with the slab sides and double-glazing).

I think it has something to do with the way the different aspects of design and manufacture fit together: the basic design and engineering of course, but also details such as the driving position, the interior trim, and the feel of the controls.

The thought came to me 10 days ago wandering round the cars on display at an auction organised by Coys of Kensington. They were selling a variety that spanned a 1926 Model T Ford (in beige, not black), a 1936 Rolls-Royce Phantom III, a sweet little 1939 Morris 8, several Mercedes including a 1956 gull-wing 300SL and a number of Bentleys, Jaguars, Ferraris and Aston Martins.

Some of the cars, while doubtless desirable to people who want to build collections, just didn't feel quite right.

The really puzzling thing was that the same manufacturer could sing and could croak. Thus there were several lovely Mercedes coupes and convertibles, but one of the slab-sided saloons. There was a brace of Aston Martin DB2/4s that were somehow sweeter to my eye than the later, beefier, more valuable and arguably prettier DB4 competition car. And why was the 1939 Lagonda V12, with engine designed by W O Bentley and built to rival Rolls-Royce, not quite the delight of the more imposing but more old-fashioned Phantom III?

A hint of the explanation came from my nephew, Christopher, who came with me. He loved all the Ferraris for their combination of style and detail -- the red camshaft covers are a touch of genius. But the Lotus Excel was given a thumbs-down for its combination of wooden dash and tweed upholstery. He loved sitting in the 1970s Bentleys, and the great thing about them is you sit so high up that you feel in charge of the world.

Thinking about it afterwards, I came to the conclusion that it is indeed the detail that makes the difference. The basic concept has to be right and the engineering has to be appropriate to the use. Cars that are under-powered or handle like pigs will always disappoint. Looks matter: the Ferraris looked wonderful, though to my eyes a Jaguar D-type replica in Ecurie Ecosse colours looked even better. But the detail makes the difference. Remember how the simple lines of the MGB were mucked up by those rubber bumpers.

And then there are the seats. Different cars need different seating positions and different seating sensations. In the Bentleys you are high up, both to be in charge of lesser mortals and to be seen to be in charge. The bench-style backrests in the DB2/4 worked surprisingly well, as do the hug-me buckets of the 3.5-litre 1934 Bentley. Rationally they ought to be the other way round, for the Aston is the more sportive. I suppose that just shows that rules are there to be broken.

That leads to the final point. There is an element in car design that is not rational. The thing that makes a car special is the intuition of the human being who signs off the final details before production. When we drive a special car we are reaching into -- and connecting with -- the mind of a special person.