"Motorists are putting themselves and others at risk by driving in unsafe footwear, a new poll has revealed.
Getting behind the wheel bare-foot, in flip-flops, high heels or shoes with poor grip, could invalidate your cover if you have an accident."
"Driving in inappropriate shoes, or none at all, isn’t illegal, an insurer could perceive it as dangerous driving and, in extreme cases, it could invalidate your insurance in the event of an accident."
http://www.mindfulmoney.co.uk/mindful-news/driving-in-inappropriate-footwear-could-invalidate-your-car-insurance/