Insurers believe that people with CCJs are a poor risk (financially insecure, more likely to default on premiums or make dodgy claims) so the Financial Ombudsman would accept that this question affected their decision on whether or not to insure you, and how much to charge for the cover. However gouldc is right - if the non-disclosure was really that important to the insurer, the correct course of action for them to take would be to avoid the policy, which means that they cancel it altogether (usually also refunding some or all of the premium) and it is as if the policy never existed. they can't just turn down the claim. If they have just turned down this one claim and have kept the policy in force then that is actually a mistake on their part and they may now be legally obliged to deal with the claim because of that. The Financial Ombudsman would probably support you.