The shots in the briefing room of Thames House in episode 6 used an angle never before used there, this was because the set was already partially pulled down when episode 6 was being filmed. The college where they were filming was condemned and due to be pulled down almost as soon as the crew left. For the second series the Grid was reconstructed at Pinewood Studios.
The Railway station "London Broad Street" was in reality closed down in 1986. The images used for it are Waterloo East, Waterloo and Marylebone Station.
At the end of episode 6 when Tom is talking to Ellie through the letter box, a giant letter box had to be used so that enough of the interior of the house could be seen through it.