I think this is wishful thinking, but I'll ask on the offchance that I'll save the £20 my own car insurance company wants for this cover...

I'm getting a courtesy car from the garage while my own car is in for some work. There is no charge for this, but I have to provide them with some evidence that I have fully comp insurance that covers the courtesy car, either in the form of a clause in my basic policy (nope) or a cover note (will cost £20 from my friends at Admiral).

Is there any way that the hire car insurance on my Amex be used instead to cover me on this? As I said, I think not but as my understanding of this particular benefit is a bit vague I thought I'd ask.