There was a case not so long ago with Highway insurance. It was quite a widely publicised case about a bloke and his heavily modded RX7. On his way to a meeting, the car started malfunctioning, so he pulled over to investigate. On doing so the car was engulfed in flames.
to cut a long story short, the insurance company initially refused to pay out because they reckoned that one of the fuel pipes on his car was non standard and as he hadn't declared it, his insurance was null and void!! Not only that, the 'engineer' they sent to inspect it had taken the piece of pipe off the car for his records. They also tried to get out of it by saying the car had been plumbed for NOS, which it hadn't. It transpired that the pipe had been replaced in Japan a long time before the guy had bought the car and had been routed wrongly so was spraying fuel over the exhaust when the tank was full.
They also tried to get out of it by declaring he was on his way to a 'race' meet. He was in fact going to a RWYB, but that had nothing to do with the claim as he wasn't taking part at the time of the incident.
They eventually paid out due to the immense bad publicity they got over the case.
They tried everything to get out of paying up!!
Highway insurance for anyone that's interested!!