The most expensive car on sale in Britain is the Mercedes-built Maybach 62. This super-luxurious limousine costs £281,380, more than any standard Rolls-Royce or Bentley. According to the Halifax bank this makes it rather more than twice as expensive as the average British house, currently yours for £127,557. By any standards it is a phenomenally expensive car.

But rewind to November 1987 and a Christie’s auction in London’s Albert Hall. There were a few cars in the catalogue that night, all extremely special. But the lot that 4,000 enthusiasts, me included, had gathered to see was one of just six Bugatti Royales ever built. This, a 1931 Type 41, the so-called Kellner coupé, was the most beautiful and we watched in awe as Robert Brooks, the auctioneer, created history. When his gavel came down the price stood at £5.5m. No car has ever fetched more at auction.

That, however, is not even close to the highest price paid for a car. Simon Kidston, president of the auction house Bonhams Europe, says: “The most remarkable story that illustrates not just how much money one car can command, but also how much can be both made and lost, is that of a certain Ferrari 250 GTO.” The 1962 250 GTO is Ferrari’s most fabled car — fast, beautiful, successful on the track yet completely road legal and eminently usable, it has been regarded for some years as among the most valuable cars on the road.

“It wasn’t always this way,” says Kidston. “In the early 1970s they cost around £5,000, less than a new Porsche 911. Back then one was bought by a garage in Sheffield that hung onto it until the absolute peak of the boom in 1990. It was then sold to a Japanese man for £10.5m. Two years later the world was in recession and the car was sold again, this time for £2.5m.” That’s depreciation at £11,000 per day.

Staggeringly, even £10.5m for a GTO is nowhere near the price paid for what Kidston is sure is the most expensive car transaction.

“The record belongs to a Mercedes grand prix car, a W196 of the type raced by Juan Manuel Fangio and Stirling Moss in the mid-1950s. Mercedes had donated one to the National Motor Museum at Beaulieu which, in 1987, asked if it could sell the car to finance the renovation of the museum. Mercedes agreed and the car was duly sold for £1.5m. The car was kept in a bonded warehouse in Switzerland until 1990 when it was sold to a French industrialist for $24m. Three or four years ago it was sold to a German industrialist for less than half that amount.”

There have, of course, also been wildly expensive road cars. Most recently Ferrari’s Enzo commanded a new price of £425,000, and yet proved so popular that Ferrari decided to up production from 349 to 399 units. Nor is it a car you placed an order for: instead you waited for the call, hoping you were on Ferrari’s list of customers considered sufficiently important to be invited to buy one.

Coming up is the £300,000 Porsche Carrera GT, the £250,000 McLaren Mercedes SLR and, the king of them all, the 1001bhp Bugatti Veyron 16.4, of which just 50 will be built and for a price well in excess of £500,000.

But the most expensive proper production road car ever sold remains the 240mph McLaren F1. It was £627,000 when new in 1994, can cost over £100,000 for a really thorough service, and commands between £800,000 and £1m today.

Rather than buying off the shelf, even a very high one, another way to spend a fortune is to have a car created to your own specification.

Aston Martin is much too discreet a company to name names let alone prices but Tim Watson, director of public affairs, fondly remembers one customer asking the factory to create a James Bond DB5. “It was identical to the real thing, complete with imitation machineguns,” says Watson.

Meanwhile Bentley produced an Arnage for last year’s Paris motor show to showcase its craftsmanship and demonstrate that it could compete with the new Maybach and the new Rolls-Royce Phantom. It had a wheelbase extended by almost 30in, a 22in plasma screen television and an interior furnished in Yorkshire oak — not veneers, you understand, but actual slabs of timber. After the show the Bentley went on a world tour but never came back. At one Middle Eastern venue a customer made an offer Bentley felt unable to refuse. It is said to have been nearly £500,000 before tax. Bentley now has five similar cars in production.

Some cars you simply cannot put a price on because they are never sold. The Queen’s new state limousine was presented by a consortium of more than 50 British motor industry suppliers headed by Bentley so its cost is unknown. However, as even concept cars for motor shows that are not required to move can cost millions, it’s a fair bet the state limousine was not exactly cheap.

As for the most valuable car in the world, Kidston is unequivocal. “Even though one has never been sold, there is no doubt at all in my mind that the holy grail is the Mercedes 300 SLR.”

This is the road racing version of the W196 grand prix car and driven by Stirling Moss in 1955 over the 1,000 miles from Brescia to Rome and back at an average of 97.96mph.

“It has everything,” says Kidston. “It’s stunning beautiful, technologically very advanced, all conquering, incredibly quick and every one is still owned by Mercedes. Not a single car has ever been released from captivity.”

How much would it fetch if one were to come to sale today? “It’s impossible to put a figure on it. In my view it is one of just a handful of cars in the world that can genuinely be thought of as priceless.”

WHAT PRICE EXCLUSIVITY?

Some of the costliest cars ever
1955 Mercedes W196 $24m
1962 Ferrari 250 GTO £10.5m
1931 Bugatti Royale £5.5m
1932 Alfa Romeo Tipo B $5.6m
1964 Shelby Cobra Daytona Coupé $4.4m

Some of the highest list prices
1997 Mercedes CLK-GTR £1m
1994 McLaren F1 £627,000
1997 Porsche GT1 DM1.5m
2003 Ferrari Enzo £425,000
1992 Jaguar XJ220 £403,000