Leaving a side any questions as to whether the insured received proper competaent profexxional advice to place him in this situation, it is necessary to recognise that the contra preferentem rule must always apply and give the insured the benefit of any doubt. It is likely that the excess clause of a policy will refer to the loss and not the claim under a particular policy. In the curcumstances it seems reasonable to conclude that one excess should be deducted and that this should be the lower of the excesses in the policies.
This will again raise the problem of a policy being called upon to contribute to a loss which is greater than its actual liability. This happens frequently.