I had a similar situation that took 15 months to resolve in my favour (although they did not take my cab off of me ).
Your mate also stands a very big chance that his insurance company will try to hold him ( at least partly responsble) for not having eyes in the back of his head........just so that they have an excuse to reduce his " No Claims Bonus" by around 2/3 years.
He needs to get as much evidence as he possibly can ( I know that is stating the obvious - unfortunately he will need it).
His insurance company may also send an investigator to his house to take a statement! Trust me when I say that they are not your mate as they would like to portray. They are there to ask (leading ) questions that may seem innocent at the time, the bottom line being is that they are trying to find a small chink of evidence that gives the Insurance company a chance to up your premium.
If the above should happen, then your mate should not be lulled into giving an answer on any question that he is not sure of - also give deep thought as to what is behind the questions. In reality they are there to try and trip you up......smiling assassins

good luck, he will need it.