Rivetted Paul! I had the same issue with an insurance company and the storm damage to our old iron roof in Brisbane. They kept insisting that it was wear and tear (some of it was 95 years old). I kept saying it didn't leak before the storm... am I not covered for storm damage (I was)? They eventually paid the lot. So Frank's neat point about "coincidence and co-incident" is maybe the key. You may be not able to absolutely prove it did not leak before the accident, but they cant prove it did? All you know is it leaked after the accident.