BBC fights to keep The Stig's helmet on

Unmasked ... Top Gear's The Stig has been revealed. Can you believe it? Source: Supplied

The BBC has taken legal action aimed at blocking publication by book giant HarperCollins of an autobiography which would unmask the faceless TV show favourite, who speeds around a race track with a blackened visor.

Clad in race overalls and a helmet, the driver's identity has long been a closely guarded show secret, spawning T-shirts emblazoned with slogans like "My Dad is The Stig".

It is claimed he is bound by a confidentiality agreement and revealing who he is would spoil viewers' enjoyment of the popular TV program, which airs on the Nine Network.

The hearing was due to take place on Tuesday in London, with the case listed as the British Broadcasting Corporation v HarperCollins and others.

The Stig famously takes to the track in an assortment of cars, as well as training celebrities to set lap times in Top Gear's popular "Star in a Reasonably Priced Car" segment.

Only a handful of executives and Top Gear presenters Jeremy Clarkson, Richard Hammond and James May are said to know who he is.

Several racing drivers have been linked to the role, including former Formula One world champions Damon Hill and Michael Schumacher and most recently racing driver Ben Collins, who was a stunt double for James Bond.

The current Stig is the second in the role. The first Stig, Perry McCarthy, was dropped in 2003 after his identity was uncovered.

After news of the legal action broke, HarperCollins criticised the corporation for using licence fee cash, paid by the public, on the moves to block the book and said it would "vigorously defend" its right to publish it.

In a statement, the publisher said: "We are disappointed that the BBC has chosen to spend licence fee payers' money to suppress this book and will vigorously defend the perfectly legitimate right of this individual to tell his story."