Sir Jackie Stewart, 85, drives F1 car at Bahrain GP with Michael Schumacher signed helmet

Sir Jackie Stewart has delighted fans with a demonstration run in one of his title-winning cars at the . Ahead of Sunday's race, the 85-year-old got behind the wheel of his 1973 title-winning Tyrrell machine.

And what made the run extra special was the helmet he was wearing as he did so. It has been signed by every living F1 champion, including who held the pen to mark his initials onto the white and tartan helmet.

It will now be sold at auction to raise funds for charity Race Against Dementia, which he founded after his wife of more than 60 years, Helen, was diagnosed with the disease in 2014.

Major F1 figures have been supportive of his charitable efforts for many years now. And a swathe of former champions were only too happy to daub their signatures onto his old helmet for a good cause.

Sir Jackie said he was particularly delighted that seven-time champion Schumacher was able to contribute, with the help of wife Corinna who guided his hand to leave his personal mark on the helmet.

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It is wonderful that Michael could sign the helmet in this worthy cause - a disease for which there is no cure," he told the . "His wife helped him, and it completed the set of every single champion still with us."

Schumacher continues to recover from the life-changing injuries he suffered in a skiing accident in December 2013. Details of his condition and medical care have remained under wraps with Corinna keen to protect her husband's privacy, meaning only a select few trusted family members and friends are allowed access.

The Stewart family has also experienced its own fair share of medical tragedy in recent years. Helen, Sir Jackie's wife of more than 60 years, was diagnosed with diagnosis in 2014 and her condition has steadily worsened over the years.

Just last week . "Just the other day it was time for dinner, she's getting up and I'm sitting close by, and she says, 'Where's Jackie?' That's the first time that's happened and that's only a few weeks ago," the Scot said.

"A bad feeling came over me." He went on to say that his wife's mind is in "a new " and that she is now no longer able to walk on her own as a result of her condition.

As well as caring for his wife, Stewart continues to be a regular visitor to the F1 paddock. But his exploits in Bahrain this weekend will be remembered for some time after driving one of his old F1 cars more than 50 years on from his retirement from the sport.