What a gash headline. Jets have been flying into Northolt for years without any disruption to LHR at all.
I suspect the only disruption to LHR would come if/when the Typhoons became airborne because of an immediate threat South of London and had to fly over/close by.
But if that is ever the case, I am sure the RAF Pilots are skilled enough to dodge the slightly bigger aircraft and slalom down the line of those on finals approaching runway 27R