"Northfields station, 2007." View eastward, towards Acton Town, Piccadilly Circus and Cockfosters: London Underground Piccadilly Line to Heathrow. The line, as far as Hounslow West was also on the District Line until 10/10/64; Piccadilly Line trains began 13/3/33. Extension to Hatton Cross opened 19/7/75, then to Heathrow Terminals from 12/77 (to Terminal 5 3/08).