On a recent early morning trip to Heathrow on the Piccadilly Line, the train I was on called at Ravenscourt Park, Stamford Brook, and the other District Line stations it passes through. These stations are not indicated on the Tube map as Piccadilly stations. Does the Piccadilly Line in fact always stop at these stations; does it only stop there in the early mornings as some kind of variant "local" service?
Update: This appears to have been the result of line closures on the District line at that time:
Saturday 17 and Sunday 18 June, no service between South Kensington / Edgware Road and Wimbledon / Kensington (Olympia) / Ealing Broadway / Richmond. ... During the day on Saturday and Sunday, some Piccadilly line trains call additionally at Ravenscourt Park, Stamford Brook, Turnham Green and Chiswick Park.