Used car buying guide: Ford Escort RS Cosworth

The Audi Quattro, Lancia Delta HF and Peugeot 205 GTi have soared in value in recent years, not just because of the surge in demand for 1980s performance cars but also because of their relationship with the most fondly remembered era of the World Rally Championship: Group B.

But what of the cars spawned from that thrilling category’s successor, Group A? Clean, early examples of the Audi Coupé, Subaru Impreza and Toyota Celica are remarkably easy to find and available for a relative pittance, but one from this period is quickly entering the upper echelons of cult car desirability: the insane Ford Escort RS Cosworth.

Here was an affordable family car modified to accelerate as fast as the Ferrari Testarossa, hit 150mph and tackle some of the most brutal terrain international motorsport had to offer.

Underneath its outlandish, oh-so-1990s bodywork are evolutions of the engine and four-wheel drive system that underpinned its legendary Sierra predecessor, with Cosworth’s revered YB turbocharged four-cylinder unit uprated to the tune of 224bhp.

The 2500 homologation specials that came first used the same colossal Garrett turbo as Ford’s formidable Group B racer, the RS200, while later cars got a less laggy smaller unit that improved usability and was a lot less prone to spontaneous combustion.

Much is also made of homologation cars’ underseat water injection system, but it was only put there so that Ford could install a turbo-cooling device in its competition cars and doesn’t make the early Cosworths superior in any way.

The Cossie’s trademark whale tail was the work of young designer Frank Stephenson, who would later prove his affinity for stylistic exuberance with the Maserati MC12 and McLaren P1. Buyers could have it deleted towards the end of the car’s life, but you’ll struggle to find an unspoilered example these days.

Three trim levels were available during the four-year production run. Motorsport got a cloth interior and little in the way of embellishments; Standard added a radio and central locking; and Lux was, as the name suggests, the best-equipped.

With its pop-out rear windows and standard-fit sunroof, the latter is the most prevalent today, with prices starting in the mid-£30,000s for tatty high-milers and rising to around £60,000 for dry-stored examples with reams of receipts and unchanged powertrains.

Untouched Motorsport cars are harder to source, having mostly been modified for use in, erm, motorsport, but they do crop up occasionally – usually finished in Diamond White and with an £80,000-plus price tag.

The YB motor isn’t rapid by modern standards but is highly tunable. The smaller turbo can handle only about 300bhp, though, so speed freaks often upgrade to the bigger one. Like many cult classics, it’s the factory-spec cars that command big bucks, so avoid any with aftermarket bodykits and energy drink logos.