[Spoilers] Interview with S9 writers Sam Vincent & Jonathan Brackley

[Silktie]

Perhaps 'Berlin Corners' is another reference to them wanting to go back to a more le Carre style of storytelling in season 10? Don't they say that on the DVD extras somewhere?

Also, Harry's 'the spy they want to kick back out into the cold.' Le Carre's The Spy Who Came In From the Cold plays out in Berlin, with the climax focussing on trying to cross the Berlin Wall.