Donald,
Not all fully comprehensive policies allow the insured to drive another car. Therefore you will need to check your insurance policy documents to see if that's allowed and you should also contact your insurer to see if your son can drive a second car under that policy. I'm not sure how this is going to work out because as a learner, you're more of a risk to insurers and therefore, the insurance company with which you've got insurance cover can forbid your son to drive another car until he gets his full driving licence. Also when the car insurance policy allows you to drive another car, it is most of the time covered for Third Party only. This means that any damage to the other car that he drives will not be covered by the insurance policy. What will be covered though is any damage to another vehicle arising from an accident when he is driving the other car. As I said before, your best bet is to get in touch with your insurer and ask them everything you need to know.
