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Sir Jackie Stewart has told Â鶹Éç Radio 5 live that treating his wife’s dementia is 'the biggest challenge of his life'.

Lady Helen, 75, was diagnosed with the disease two years ago. Her husband is now launching a charity called Race Against Dementia to put right what he sees as a grave lack of research funding.

The former three-times Formula One world champion spoke to 5 live Daily's Adrian Chiles about how his racing career was easy compared to tackling dementia.

"It's the biggest thing I've taken on, that's for sure. When I was a racing driver, God gave me a gift to drive cars. That was easy compared to what I'm challenged to here."

This clip is originally from 5 live Daily on 5 July 2016.