The series was a strong influence behind the 1997 film "Austin Powers: International Man of Mystery".
This episode takes place in 1902 and 1966.
Though this is a BBC production, during a rooftop sequence, a full establishing shot shows the Headquarters for Granada, complete with a giant sign of their logo.
John le Carré's 1965 spy novel 'The Looking Glass War' is visible on the book shelf above Georgina's bed.