How Ford’s Sierra Cosworth went from £20,000 eighties boy racer to prized collector’s item worth £200,000 today

The wealthiest classic car collectors often bargain at auction rooms to get their hands on the rarest, most exclusive and most desirable models of bygone eras.

Aston Martin, Bugatti, Bentley, Ferrari, Jaguar, Lamborghini, Porsche, Rolls-Royce: just some of the names that traditionally attract the most attention and bid the highest from the richest petrolheads looking to add valuable engines to their garages.

But when it comes to cars that have recorded the biggest increases in value in recent years, one of the mainstream brands is putting its lavish counterparts to shame: Ford.

High-performance ‘Fast Fords’ from the seventies to the nineties have become serious collector’s items in recent times, and none more so than the Sierra RS Cosworth.

The souped-up family car of the eighties cost up to £19,950 in showrooms forty years ago. That’s around £59,500 in today’s money inflation taken into account.

But if we wind the clock forward to today, wealthy enthusiasts are willing to invest six-figure sums on the best surviving examples.

Six Sierra Cosworths will go under the hammer at an auction in Northamptonshire later this month. Collectively, they are estimated to sell for an eye-watering £1 million.

Which begs the question: How did the market get to a situation where an eighties hot hatch is worth the same (if not more) value than a Jaguar E-Type?

The Sierras heading to the block on Friday, July 24 and Saturday, July 25 include a diverse but highly valued selection of the nameplate.

It will probably be three of the limited-edition RS500 Cosworths that will cause the wildest bidding; only of these – yes you guessed it – 500 units were produced in the four-month period between March and July 1987.

The most valuable one is one of the last examples; number 468 – CDB registration E84 – one of 56 officially painted white.

The vast majority (392 cars) were black, with the rarest color being Monsoon Blue, of which only 52 ever rolled off the assembly line.

The car has covered just over 26,700 miles from new, making it one of the least used examples still in existence.

It formed part of the BonkeRS Collection, which is considered the most well-known private collection of important Ford RS models in recent years.

Also featured in Dan Williamson’s 2016 book Factory Original Ford RS Cosworths as ‘the benchmark example of originality’.

Iconic Auctioneers, which is hosting the sale at Silverstone racetrack at the end of the month, believes it will trigger bids in the £150,000 to £200,000 range.

The top pick of the six Ford ‘Cossies’ going on sale later this month is this white – low-mileage – RS500, which Iconic Auctioneers says will sell for between £150k and £200k.

A second example – registration E454 EFV, in black and number 195 out of 500 – is another engine from the BonkeRS Collection.

Long-term early ownership is backed by RS500 Registry approval, original factory literature and service history covering 44,599 miles to date.

Guide price is between £80,000 and £100,000.

And the color that completes this trio is the most special color: the blue RS500 number 470 of the E111 UD9 registered output.

It, too, has been under long-term ownership and is almost entirely original, despite having covered 67,260 miles over the last 40 years.

Estimated at £90,000 to £120,000.

This black Ford Sierra RS500 Cosworth with just under 45,000 miles is expected to attract bids of £100,000

The rarest color of the Ford Cosworth RS model, of which there are only 500 units, is Monsoon Blue. This example is estimated to fetch up to £120,000 when it hits the block

Surviving competition RS500s are very rare, so this ‘Group A’ Australian and British Touring Car from the late 1980s is expected to sell for almost half a million pounds.

An RS500 competition from the famous Group A racing series, which competes in both the Australian and British Touring Car Championships, is also on offer to the highest bidder with a guide price of between £400,000 and £450,000.

Also offered is a non-RS500 1987 Ford Sierra RS Cosworth in Diamond White – registered D404 BAB – with single-family ownership, just 6,242 miles from new, and a remarkable level of originality.

The three-door Cosworth, which was first registered in 1987, spent its first 37 years with its first owner before being passed on to his son.

It was placed in private garage storage in 1988 and still displays its 1988 tax disc today.

The facility reopened briefly in 2015 and again in 2025 and has only undergone ‘sympathetic maintenance’ since then.

Its incredible originality and time warp condition means it could eclipse some of the rarer RS500 examples with an estimate of £100,000 to £120,000.

The Ford Sierra Cosworth, which is not the ‘standard’ RS500, is also becoming an increasingly valued asset. This 6,242-mile example has a guide price of £100k to £120k on the bodywork

The sixth of the Coswroth cars offered at auction to the highest bidder is this rare 1991 Sapphire Cosworth sedan, one of only two examples officially tuned to survive.

The last of the six Sierra models is the 1991 Sapphire Cosworth Rouse Sport 304-R – registered J88 COS – one of racer and tuner Andy Rouse’s unicorn road-going Sapphire Cosworth conversions.

Rouse built the car for the racing team’s doctor, Dr Roger Melhuish, and it has been kept in his garage since new.

Adding to its desirability, it is believed to be one of only two surviving examples of the Diamond White 4×4 currently registered in the UK and bidding is expected to exceed £50,000.

Commenting on the availability of the ‘Cossies’ collection, Iconic Auctioneers auctioneer Rob Hubbard said: ‘Performance Fords continue to generate a great deal of love and serious collector interest, and this group of Sierras is a great reminder of why.

‘From highly original road cars to Group A racers with period touring car pedigree, these are cars that appeal to enthusiasts of all levels.’

The RS500 was announced in July 1987 and featured an upgraded Cosworth engine with power increased to 224 hp, upgraded bodywork and the ability to be hand-assembled.

Ford Sierra Cosworth: a brief background

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 way to get the Sierra approved for Group A Touring Car racing, with the requirement that 5,000 cars be built and sold before the competition version hits the track.

Launched in July 1986 and based on the three-door Sierra body, it was designed by Ford’s Special Vehicle Engineering (SVE) and powered by a now legendary Cosworth-designed 2.0-litre turbo engine.

At the time, the Sierra Cosworth was a new breed of performance car; He was a ‘blue-collar hero’ who could humble real sports cars.

The RS500 was announced in July 1987 and featured a mechanically improved Cosworth engine (more like the engine that would be used in competition), increased power to 224 hp, modified bodywork and the ability to be hand-assembled.

This makes the RS500 the best Fast Ford of the 1980s in the eyes of enthusiasts and classic car collectors.

A total of 5,545 cars were produced, of which 500 were sent to Aston Martin Tickford to be converted into the Sierra ‘RS500 Cosworth’.

If the RS Cosworth was a homologation car, the RS500 was an evolution special.

Once Ford produced the required 5,000 RS Cosworths, Group A rules allowed an upgraded ‘evolution’ model to be launched.

This could include changes focused on increasing racing potential, provided Ford sells 10 percent of the original number of cars as road cars and thus uses the 500 tag.

When a Ford Sierra Cosworth RS500 enters an auction room today, it often triggers a bidding war among collectors.

Eye-watering prices are being paid today

The value of the RS Cosworth – especially RS500 examples – was increasing significantly in the 2010s and early 2020s.

But in 2022, prices really started to rise.

Iconic Auctioneers (formerly Silverstone Auctions) sold a ‘standard’ Sierra RS Cosworth for a staggering £132,750 in November that year.

The winning bid for the car, which was completely original and had less than 9,000 miles on the clock, was £10,000, breaking the previous record.

But that was the February 2023 sale. The E378 TKN registration really inflated the cost of these cars.

A 5,192-mile example of the sought-after RS500 sold for £596,250; This was 30 times the original showroom price in the 1980s and more than four times the previous record set just three months earlier.

The auction house described it as ‘perhaps the finest surviving example of the rare Sierra Cosworth RS500’.

In an expert column written exclusively for the Daily Mail and This is Money, classic car valuer John Mayhead described the 2023 sale as an ‘outlier’ that may never be repeated again.

However, it is obvious that the price paid three years ago has brought the general value of these vehicles higher than ever before.

John explains: ‘The RS500 was the final homologation of the Ford Sierra and is rightly prized by collectors.

‘Prices reached their peak thanks to Iconic Auctioneers’ major one-off sale of a low-mileage car in February 2023, which netted around £600,000, although this price has hardly been reached in recent years except for full race cars with good track records.

‘The gap between fair examples and the most original and pristine ‘concours’ examples has grown significantly over the last decade, with collectors scrapping the best examples.’

Iconic Auctioneers sold two RS500 examples for over £100,000, although it was a long way off the record of £596,250 in the last two years.

To put this in perspective, the average selling price in the sixties The price of a Series 1 Jaguar E-Type today typically ranges from £70,000 to £150,000.