Few if any motorsport formulae can match the sheer drama and excitement of the controversial Group B Rally era, one which brought hitherto unseen levels of supercar performance to the special stages.

Although the formula only existed for four years, its impact on both the sport and the wider consciousness was wholly disproportionate.

Having won only one round of the World Rally Championship in 1984 with its ageing two-wheel-drive 037, Lancia opted to develop a replacement for the final round of the 1985 Championship onwards.

Dubbed the Delta S4, the new car bore a distant resemblance to its road-going counterpart; although, in predictably outlandish Group B fashion, it would replace the standard Delta’s steel monocoque chassis with a carbon-fibre-clad tubular spaceframe, in which the engine was relocated to the rear.

The S4 also employed an ingenious ‘twin-charging’ system, whereby a supercharger operated in sequence with a turbocharger to reduce turbo lag and improve driveability,...