Common sense, which, contrary to popular belief, prevails in courts and even with lawyers and insurers, suggests the other side's version is so implausible as to be laughable. Don't know about others, though it would probably be common experience, but in 50 years of driving I have never seen anyone reverse suddenly when at a roundabout and hit a car behind but I've seen or heard of dozens of rear end shunts when the driver behind runs his vehicle into the car in front. It's the quality, not the quantity, of evidence that matters. Where were these 'witnesses' found ? Did you see them ? Worth these worthy citizens just passing by, and took it upon themselves to find the name and address of just the one driver so they could nobly explain his actions in court months later? Yeeeees, as Mr Paxman would say !