You really should declare any ailment you are having treatment or medication for, or have had treatment for, as Angela said.... if you need any treatment and it is in any way connected to your ailment, ie Phil, if Jen had a fall.... your insurance would not cover you.
My baby brother had a kidney removed when he was three years old because of a non malignant tumour, he has neither medication or check ups, he is now fifty years old but has always declared this on his insurance, if he got an infection in his other kidney whilst on holiday and needed treatment his insurance would be void if he didn't do so.
Anyone whose insurance comes with their bank account should check very carefully what they are actually covered for, as some of these policies are not worth the paper they are printed on.