Looks like the RAF to me
The Red Arrows aren't the only ones who fly formations. There were a number of fly-pasts of Buckingham Palace last summer (Queen's Birthday and RAF Anniversary as good examples) and each used formations of planes just like that.
As further proof, trace a line from the Palace, up the Mall, and you'll find it goes very close to that spot. Chances are it's a formation of Tornados or Typhoons on the run-in.
Biting the hand that feeds IT
