The original Ford Sierra RS Cosworth was the first Ford to wear the Cosworth badge and was presented to the public at the Geneva Motor Show in March 1985. It was introduced as a means of homologating the Sierra for 'Group A' Touring Car racing, with a requirement that 5,000 cars were built and sold. Launched for sale in July 1986, and based on the three-door Sierra body-shell, it was designed by Ford's Special Vehicle Engineering (SVE) and was powered by a Cosworth-designed 2.0-litre turbo engine of now-legendary repute. At this time, the Sierra Cosworth was a new kind of performance car - a 'blue-collar hero' able to humble true sports cars! In total 5,545 cars were produced - of which 500 were sent to Aston Martin Tickford for conversion to the Sierra 'RS500 Cosworth'. If the RS Cosworth was a homologation car, the RS500 was an evolution special. Once Ford had built the requisite 5,000 RS Cosworths, 'Group A' rules allowed an upgraded 'evolution' model to be launched. This could carry changes focused on improving its racing potential, provided Ford sold 10% of the original number as road cars, hence the 500. The RS500 was announced in July 1987 and had a mechanically uprated Cosworth engine (more similar to the one to be used in competition), with power boosted to 224bhp, modified bodywork and the cachet of being hand-assembled - the RS500 really is the ultimate 1980s Fast Ford! Around 14 years ago, our vendor, a knowledgeable and particularly fastidious enthusiast, decided that he would like to add an RS500 to his Collection. He knew what he wanted but took the precaution of enlisting the help of a friend who was a marque expert. They considered a number of cars, including some lovely examples, but were focused on finding the best RS500 they possibly could. A number of other contenders were rejected until, one day, E378 TKN appeared and was unquestionably 'the one'. Its originality was unmatched, the mileage was nominal (even today it has only covered 5,192 miles) and it had patently been cared for. Although very lightly used during our vendor's tenure, it was regularly serviced and maintained during this period by Tremona Garage of Southampton, a local specialist widely recognised as being hugely knowledgeable when it comes to Fords from the 1970s, 1980s and 1990s. They are also known for preparing cars to a Concours standard with much success in the Autoglym Masterclass and others. Who better to entrust with an RS 500 that may well turn out to be the best and most original RS500 to come to market. The attention to the detail of this car's maintenance cannot be understated. Our client has impressively managed to source a supply of rare new/old stock oil filters, fuel filters etc. so, not for this car a modern oil filter of the correct type, but an original orange one that would have been supplied when new. This 'forensic' attention to originality can be illustrated by our vendor's purchase of a set of period RS 500 wheels and tyres in order that TKN's date-stamped originals can be carefully stored and not have to bear the weight of the car for prolonged periods. This diligent approach is typical of our vendor and will explain why this gleaming black RS500 may well be the best you have ever seen. In 2022, Tremona carried out a full re-commissioning service on E378 TKN including the replacement of engine oil and filter, spark plugs, fuel filter, cambelt and a new battery. All parts used are genuine new/old stock parts and are identical to parts fitted at the factory. The engine oil filter is a Fram PH2854, spark plugs are Motorcraft AGPR 901C and a black Weber fuel filter was fitted. All these parts have not been available for many years and have been sourced to maintain the car's originality. As mentioned, the original Dunlop D40s are on the stored wheels, the original Ford exhaust system is still in place, the factory fog lamps remain in the boot awaiting fitting by the dealers and there is a file full of history detailing the car's life. Recently refreshed and with a fresh MOT, E378 TKN will be presented at Race Retro on its original wheels. Silverstone Auctions are proud to have been involved in the sale of many cars at World Record prices, many of them Fords. With 'Fast Fords' seemingly knowing no bounds in their desirability, and this one believed to be the very best example of the ultimate 1980s Fast Ford, we invite and encourage any serious collector to inspect this superb, 5,000-mile Cosworth as its type is unlikely to be found again.