It just depends on your policy. Some policies have an unlisted driver excess that costs more than the normal excess and will fk your premium up next year (if you don't have rating 1 protection), whilst others don't insure drivers who aren't on the policy. If this is the case, as the owner of a comprehensively insured vehicle, you can make a claim and the insurance company will pay out on it...but to my knowledge, they will then go after your mate for the costs.
This is one reason I don't make a habit of driving other people's vehicles, unless they A. have the former policy, B. I'm listed on their policy, or C. they are in the vehicle to be able to take the fall if you have an accident.