A one-off Ferrari has been uncovered rotting in a Japanese barn - and it's worth a staggering £1.5million.

The unique Ferrari Daytona was found in filthy condition after being left for 40 years.

6 Ferrari Daytona was once the fastest car in the world with 174mph top speed Credit: SWNS:South West News Service

6 This Daytona - found hidden in a Japanese barn - is expected to sell for £1.5m Credit: SWNS:South West News Service

But not only was it once the fastest car in the world, this legendary model is the only one ever made with an aluminium body.

The Daytona was capable of 174mph when it went on sale in 1969.

Around 1,200 standard Daytonas were built over a four-year period along with five competition cars for endurance racing.

Ferrari also commissioned just one street version of the Daytona with an aluminium body - and very few people are aware of its existence.

But it has now emerged after being left to gather dust and dirt in a lock-up in Japan.

The one-off Ferrari, once a bright red sports car, is a tired-looking classic in desperate need of an overhaul having been hidden since 1980 - but it is set to create a storm among collectors.

6 Only a handful of collectors ever knew about its existence Credit: SWNS:South West News Service

Acclaimed Ferrari historian Marcel Massini flew out to Japan to inspect the car, where he confirmed its identity.

He said: "What a super scarce Daytona barn find, the only remaining aluminium-bodied production GTB/4, sold new to Luciano Conti, a close friend of Commendatore Enzo Ferrari."

The Daytona has now been shipped back to its birthplace, Maranello, Italy, where it will be sold at auction.

It is being sold without reserve, which means it could go for anything, but the auction house has given it an estimate of around £1.5 million (Euro 1.7m).

6 Interior is in poor state after being left for 40 years Credit: SWNS:South West News Service

Whoever buys it is then left with a number of options - they can get it running but preserve its 'barn find' condition or restore it to concours condition.

And as a special, storied Ferrari it will be welcome at shows around the world.

RM Sotheby's described the Ferrari as "a unique car that no other collector can claim ownership to".

The auction house said: "This Daytona holds distinct ties to its competition brethren yet never turned a wheel in anger and was instead preserved for decades.

"Presented here in remarkable unrestored condition, having been domiciled for many years and never significantly refurbished, there is no better Daytona for the discerning connoisseur, as it offers limitless opportunities for enjoyment."

Under the bonnet of the Daytona is a 4.4-litre V12 engine which developed around 350bhp when it left the factory in 1969.

This would have given the sports car a 0-60mph time of 5.4 seconds and a top speed of 174mph .

The first owner, Italian publisher Luciano Conti, took delivery of the car in June 1969 and kept it for one year before selling to its second keeper who re-sold it one month later.

6 Stunning car is the only Daytona with aluminium body Credit: SWNS:South West News Service

It was later sold to a Japanese buyer who sold it on to its current owner in 1980, who hid the car until earlier this year.

The "fabled" Ferrari, which has been driven just 22,500 miles in 48 years, was only known by a small number of collectors who tried and failed to buy it on a number of occasions.

6 The car will require a hefty restoration job to bring it back to former glory Credit: SWNS:South West News Service