Gran Turismo first appeared on the PS1 seven years ago and from the off was at the cutting edge of the racing game genre. There then followed three new versions, each raising the bar higher and selling over 30 million copies.
The driving force behind this phenomenon is Kazunori Yamauchi. Joining Sony in 1992, he worked on Motor Toon Grand Prix. During this time he started to develop the idea of the ultimate racing sim.
In 1996 he began work on the first GT and the game was released in December 1997. It was a huge success - first-year sales were 6.2 million.
Yamauchi left Sony in 1998 and set up his own development house, Polyphony Digital, which would continue to develop the GT franchise with Sony.
The original GT is the solid foundation on which the whole franchise is based. In many respects it was ahead of its time with two modes - arcade mode with forgiving handling and instant action, and Gran Turismo mode with various race options, upgrades and tougher challenges.
The success of GT had attracted car makers to video games for the first time. By the time GT2 was developed there were 600 cars from 30 makers, some concept cars including the BMW M5, and 30 tracks on which to race them.
GT2 was so big that the European release had to be on two discs. Graphically it was only slightly better than GT because of the limitations of the PS1.
The arrival of PS2 with its greater processing speed gave Polyphony the opportunity to enhance the franchise - which they did with GT3. Stunning graphics and a new physics engine gave more realism such as sun glare, particle effects and unprecedented effects in car handling.
GT4 was always going to be a challenge. It needed to surpass the excellent GT3 and expand the series. Polyphony assembled a staff of 70 whose skills had been honed in developing the previous titles.
The data for GT4 had to be collected for all the cars in the game. Manufacturers provided CAD and telemetric data - and about 500 photographs per car were taken. The real challenge was getting data on the historical models.
GT4 has 50 tracks, half of them existing. To maintain realism the data-gatherers used up 30,000 photos and hours of video footage to produce digitally accurate images of the real circuits.
The new physic engine in GT4 gives each car its own characteristics, with a huge amount of variables such as driver action, speed, braking and tyre. Even in a power slide, you're still in control and your actions determine the outcome.
The actual driving end of the game is excellent, with enough action and options to keep old hands and novices revving away.
GT4 offers a virtual garage full of the world's most desirable cars in a range of colours. You don't have to worry about not starting on a cold January. When you feel like a change, you just abandon that car and go and get yourself another without worrying about an insulting trade-in offer from a car dealer.
GT4's customisation of cars is also a major draw - just look at the number of customised cars being driven these days by "boy racers" (unfortunate label for dedicated car enthusiasts who happen to be young). It's a far cry from the time, not so long ago, when sky-high insurance meant that the best a young driver could hope for was to be a named driver on the mother's Starlet.
Whether you have a car or not, Gran Turismo 4 lets you express yourself with a flamboyance you'll never match in the real world.