Next month a truly unique piece of motorsport history - a 1953 Austin-Healey 100 Special Test Car - will be presented for auction by Bonhams more than 40 years after it was last seen in public.

As you'll see from our exclusive video, the car may not look like much but Bonhams expects it to fetch upwards of three-quarters of a million pounds. So, what's the story?

NOJ393 was one of only four Special Test Cars built by Austin-Healey. Intended as an 'insurance vehicle', it was assigned the identity of its sister car NOJ391 after the latter was forced out of the 1953 24 Hours of Le Mans because of a road accident with a local farmer. So, NOJ393 was brought into service and initially ran at that year's Le Mans with the wrong registration details, where it finished third in class and 14th overall.



The car came third at Sebring in 1954, finished sixth in the 1954 Bahamas Speed Week in Nassau and was specially converted to run in the Carrera PanAmerica the same year, where it received disc brakes, and uprated engine and gearbox and distinct fettling to the bodywork.

But it was in the 1955 Le Mans race that the car, which was now uprated to 100S specification, would be indelibly marked in racing history because of its involvement in the worst accident to have befallen motorsport. More than 80 spectators were killed when the Mercedes-Benz 300 SLR of Pierre Levegh flew into the packed enclosures on the pitlane straight after colliding with this Austin-Healey, driven by Lance Macklin.

Both the car and Macklin survived the accident and once the car was returned to the Austin-Healey team by the French authorities, the car entered the UK club racing scene before being bought by the current owner, who has kept it behind closed doors since 1969.

As a result, our video is believed to be the first footage of the car since that accident 56 years ago.

The car will be part of the Important Collectors' Motor Cars and Automobilia sale at Mercedes-Benz World on 1 December.

To find out more about this unique example, visit the Bonhams auction listing.