I doubt very much that Prince Philip came out of that accident physically unscathed. It sounds as though he avoided any significant injury, thank goodness, but any time airbags and other passive restraint systems deploy, there are physical effects on the driver and passengers. At a minimum, he is going to be sore/stiff for several days, and if he is less lucky, there may be other effects that show up over time.
I'm very glad that he and anyone else in the car survived, but much as I hate to say it, it might be time to reconsider if at his age driving on public roads is a good idea. No matter how alert he is, the reaction times cannot possibly be as good as they were 20-30 years ago.