The evidence gathered after an accident will include that relating to a driver's control (or otherwise) of a vehicle, and that could include mode of dress just as much as physical condition, illness, drink/drug influence etc. I did not have the rapacious lawyer in mind, but he too will be minded to exploit such evidence as may be presented. The law does not contain specific 'clothing' offences but the Highway Code (notably Rule 97) is always relevant when considering the conduct of a driver/rider. I rest my case.