The Audi quattro is 40 this year. In 1980, it changed the world. Yes, it helped remake world rallying in its own image - but it also redefined the nature of everyman performance cars. The democratisation of power that gave us 400hp hatchbacks can be traced back to Ingolstadt's all-conquering coupe. Yet its origins were comparatively modest: the idea for an all-wheel drive coupe famously occurred to Audi engineers surprised by the giant-killing capabilities of the Jeep-like Volkswagen Iltis being built for the German army.
Because this was VAG in the late seventies, the concept was brought to life with what the team had to hand. Audi was already developing the turbocharged 2.1-litre five-cylinder engine for the 200 5T and the basic layout of its cars, with a longitudinal engine and a gearbox just behind the front axle, was easy to adapt to four-wheel drive. The gearbox output shaft simply had to be extended towards the rear and a tail shaft and final drive assembly added. And all the necessary extra driveline hardware could be pinched from the Iltis.
The Audi 80 floorpan and basic bodyshell from the forthcoming Audi Coupe were chosen, even though the 80's dead axle rear suspension wasn't compatible with the all-wheel-drive system. It was ditched, replaced by the front subframe and MacPherson strut suspension turned through 180 degrees, with rigid track rods holding the steering arms (and allowing for rear toe-in adjustment). Audi 200 drive shafts and disc brakes were used front and rear, and the new power-assisted steering being developed for the Audi Coupe was specified.
Initially, Audi tried to get away without having an inter-axle diff and, although the high-speed performance of prototypes (even with a mere 160hp) was good enough to keep a Porsche 928 honest around Hockenheim, there was too much tyre scrub in the slower turns and when parking. A light, compact and cheap fix was to adapt the diff from the Audi 50/VW Polo and add it to the back of the gearbox. Dog clutches within this diff (and the rear one) locked them up on the move at any speed.
The all-wheel drive hardware weighed just 165lb more than a light front-drive system and only 70lb more than a rear-drive layout, while the anticipated mechanical efficiency losses never materialised. Audi discovered that tyres generate less rolling resistance when driven gently than when freewheeling. Prototypes went faster when driven by all four wheels than when the rear driveshafts were removed.
Audi took the result rallying almost straight away as a development model, and introduced the road car to customers at Geneva (having already given 'a few fortunate hacks' - Viv's words - a memorable preview the previous winter). Its impact was almost immediate: Michele Mouton became the first woman to win a WRC event in 1981. By 1983, the fast-evolving quattro was good enough to win back-to-back championships.
Its legend has hardly dissipated in the intervening years. A decent, high-mileage version can easily set you back £50k; if you want a limited-run Sport quattro, complete with shortened wheelbase and a 306hp motor, you're talking mid six figures. The car driven by Dan on a less than glorious morning in Wales is of the earlier vintage: a left-hand-drive 1981 model in UK spec, sold before Audi had completed the necessary conversion work for the rest of the world. Consequently, it's the iconic blueprint: five-cylindered, turbocharged, 10-valved, all-wheel-drive, squared off like a shipping container and quite, quite fabulous. Enjoy.