Originally Posted by
RiSq
something big went into LHR and judging the amount of helicopters I'm guessing it was AF1
I'm not sure what you mean by "something big".
Obama's VC-25 is a 747, it's no bigger than any of the couple of dozen 747s that you may have seen landing at LHR today.
The helos (VH-3, VH-60) normally precede POTUS's arrival by a day or so.