My car was subject to a very minor accident whilst parked car outside my home, whilst a third party was attempting to park. The damage was very minor (possibly none to theirs and a small mark on my bumper) so I suggested, and we agreed, the third party get a mobile specialist to spray my bumper without insurance companies involved. A month later, still no repair or contact so I notified my insurance company and put in the claim. They were informed that my wife witnessed the lengthy parking debacle so requested she make a statement, which she duly did. My vehicle was subsequently repaired successfully. 10 months later and after the third party claims to have never had the accident and with an engineer's report to suggest that there is no damage on his bumper so couldn't have caused damage to another vehicle, my insurance company has informed me that my wife's witness statement cannot be upheld because of her 'vested financial interest' and is now holding me at fault and so demanding my £500 excess. Do you have any advice for me please?