Originally Posted by
Heathrow Harry
its a piece of Russian owned machinery on UK soil
It looks a little bit interesting, really.
Under ICAO, it seems in a number of respects an aircraft is a national of the state in which it is registered. In some respects it resembles territory.
It has various protections by legal convention that would not apply if it was just an ordinary piece of machinery.
Expect others are more expert on all the legalese here.
Accept this wouldn't prevent it being searched, and wonder if it really was.