Northolt was BEA's London terminal until LHR Central was phased in. Ambassadors and Viscounts were first there, Vikings split between the two, 4/50-last Northolt service, 30/10/54.
. . . although Pan Am landed a 707 at Northolt in 1960 - the crew were headed for LHR R23 & got themselves into a bit of a muddle.