Just read the thread below and thought it important enough to start a new one just in case anyone misses my comments.
The problem with pre existing conditions is when you do not declare and then need to claim for something totally separate and different. If the claim is substantial, then the insurers and their assessors will most certainly contact your doctor for a medical report and the questions they ask are quite wide ranging. If they then find you have not declared a pre existing condition, irrespective of the relevance to your claim, they will try and use that as an excuse for not paying you. Basically they will say you have been dishonest in your application.
Lets face it, it is the substantial claims that we are most concerned with, so please never ever not declare something that could affect a future claim.