The concept car is the motor industry at its most expressive and ostentatious. An opportunity for designers to demonstrate their creative flair and fulfil their raison d'etre without common sense steering them into the grassy verge of cost and practicality.

Of course the designers' lot is not all walnut dash and carbon fibre trim. Financial considerations aside, there are a great many factors slamming on the creative brakes before the first line is even drawn. Engineers will insist on immutable technical specifications, while governments and independent bodies lobby car makers to incorporate increasingly sophisticated safety features.

All this can leave the humble designer working with his hands tied, securely strapped into a lumber-supported bucket seat with a face full of airbag. So to prevent the CAD clan going all Vincent Van Damme and cutting off their ears with Stihl saws, the car industry has nurtured a platform for the ultimate in style, beauty and aestheticism, a playground for the jaw-dropping (im)possibilities of car design - the motor show concept car. Cars so beyond the pale that the cost of making one let alone owning one ensures their existence is as fleeting as the latest celebrity fad diet. If these vehicles ever made it to the showroom even Bill Gates would balk at his car insurance premiums.

Concept cars are by no means a recent phenomenon, especially given that the car itself is only just over a hundred years old. Since the 1950s motor shows have witnessed the introduction of far-reaching new ideas and leaps of faith in vehicle styling. Generally credited to the 1950s General Motors design guru Harley J. Earl, the concept, or show car, is a 'vehicle' (pardon the pun) for designers to not only showcase their talents and massage their perfectly aerodynamic egos, but also to gauge the reaction of industry peers and the general public to the leading edge of style and sophistication.

The concept car is a challenge, a gauntlet around the cheek of acceptable decency in motor car production. Who says you can't put gull-wing doors on a people carrier. But this isn't simply an exercise in self-indulgent futility. The sleek curves and esoteric features of a concept car can capture the imagination, and some years later the remnants of those visionary ideas may appear on the latest mass-produced hatchback. However, by the time it reaches this stage, safety legislation, engineering practicalities and shareholders' spreadsheets will have twisted this once beautiful creature into a hollow unit of sale, marketed toward the Xbox generation with two years free car insurance at only 7,995 on the road.

Yet it is the aesthetic beauty and sheer boldness of the very best concept cars that really give them merit. Like the quixotic creations that drift down the catwalk of Vivienne Westwood fashion shows, it is not simply about pushing boundaries for the sake of it. It may be true that some dilute version of a groundbreaking design could appear at a later date, but it will never be as aesthetically pleasing as the one we all drooled over at the motor show. It will have airbags and child locks and headlights at some government approved height. It doesn't matter that even the world's biggest manufacturer would need a loan the size of Geneva to build just one of these masterpieces of madness, they fact is they still have value in their own right. They make grown men (and women) go weak at the knees at the very sight of them. We imagine what a world would be like where people actually drove cars like this, where we actually owned cars like this. Like a great work of art we respond with feeling and passion, and we gasp in wonder, to put it quite simply, we all turn into Jeremy Clarkson.