An example of the car that carried Button to his F1 crown in 2009 is set to go up for auction as part of the Miami Grand Prix in May.

Button famously won the title with the hastily rebranded Brawn GP team following Honda’s withdrawal from F1 at the end of 2008.

Bought for £1 by its former team principal, Ross Brawn, the burgeoning squad secured a supply of Mercedes power units which it bolted into the the Honda-designed car.

Its secret weapon, however, was an innovative design at the rear of the car, dubbed the ‘double diffuser’, which exploited a loophole in the technical rules and saw the Brawn GP car dominate the early rounds of the 2009 season.

However, with the squad operating on the shoestring, its performances faded as the year wore on and rivals caught up.

After winning six of the opening seven grands prix of the year, Button only stood on the podium twice more for the balance of the season.

He ultimately sealed the title at the Brazilian Grand Prix, heading Sebastian Vettel.

Brawn also emerged victorious in the constructors’ championship.

At the end of the year, the squad was sold to Mercedes with Brawn staying on before stepping away at the end of 2013.

Understood to have made six cars over the course of 2009, the very first Brawn BGP001 chassis is now set to go under the hammer.

According to Bonhams, which is auctioning the car, “At the conclusion of the 2009 season, the championship winning chassis (02) went to Ross Brawn while Mercedes received chassis 03.

“Due to a clause in his contract, chassis 01 was gifted to World Champion Jenson Button, remaining in his private collection until 2024.”

Mercedes had initially offered to build Button a replica claiming that no chassis was available to gift him.

“We have no spare 2009 chassis as limited quantities were manufactured for the 2009 season for cost reasons,” Mercedes wrote to Button at the time.

That prompted a legal challenge but the matter was resolved without court action with Button receiving an example of his title-winning machine.

However, there are some question marks around the chassis in question as contemporary reports claim Button instead received BGP001/02,which he drove in the Brazilian GP weekend when he sealed the title, and not BGP001/01 as Bonhams has claimed.

Whatever the case, chassis 001, the winner of the 2009 Australian Grand Prix, is the only Brawn GP machine that has been publicly offered and will go under the hammer on May 3.