I realise that Mike, my point was for something like the US registered Harrier. Everything conforms to something somewhere – its just a matter of where and finding a way to get it accepted. There are civil owned aircraft working on military contracts, so maybe that would provide a way for something like a Harrier to participate. Or finding a way by which a foreign registered Permit aircraft could operate over here in a way that is satisfactory to the authorities. I doubt it will happen anyway, as not only are RAF/MOD extremely risk averse as you point out, it also costs more than they will want to spend.

But its a nice little daydream..