Isn’t that the “Doomsday” 747 varient? So called as usualy when they’re in the air, there be trouble ahead? Last seen flying over New York on 9-11?

The E4B is an airborne comand post that is usually close-by when the US president or other very senior members of US government are out and about – when the president has visited the UK with a high-profile arrival at somewhere like LHR, the E4 has quietly snook into somewhere like Mildenhall. Not sure why this one would visit LHR though.

Andy