Not technically illegal, if footwear inhibits your ability to control your vehicle and puts you or other motorists at risk - then it is deemed illegal. If caught you may be handed a £100 fine, which can rise to £5,000 if the case goes to court. If footwear or clothing contributed to an accident that resulted in death or injury, the penalty could be considerably greater. While it is not illegal to drive barefoot in the UK, you won’t have the same braking force as you do with shoes, so it’s not recommended