Indeed, what FMS said is correct if there are trying to drive it 3rd party on the back of a fully comp policy. But if they haev insured it, in there name, with you are the owner/registered keeper. then they have have done just that.
Not sure what you're getting at there about fully comprehensive. That doesn't really come into it.
The point I was making is that I - along with thousands of others - have a policy which explicitly refers to my own car and also allows me to drive anybody else's car. So if you had a car which was sitting on your driveway taxed, but you had no insurance, it would be perfectly legal for me to drive it because the required third-party liability cover would be provided by my policy.
The only thing which has changed with the new legislation is that you (as the registered keeper) would be liable for prosecution for having the car taxed but not having insurance. But I would still not being committing any offense by driving it, since it's taxed and I would be insured under my own policy.