The Pryors, East Heath Road, Hampstead - Smiley's People Location
The flat where Vladimir was due to meet Mostyn (and where Smiley, Lacon, Strickland and Mostyn subsequently meet) is on the edge of Hampstead Heath – The Pryors, East Heath Road. These flats were built in the early 1900s on the site of an original farmhouse owned by the Pryors family.
In an upcoming interview to be published here the actor Stephen Riddle, who played Mostyn in episode one of Smiley's People, has confirmed that the interior scenes were also shot at this location.
In these photos we can see Smiley leaving the flats and then walking down Lime Avenue (the path with trees on both sides) searching for clues about Vladimir's murder.
We are fortunate that in 2014 Nigel Rumble visited the location and put together a short video featuring The Pryors, Lime Avenue and the pavilion. (The pavilion is about a ten minute walk from East Heath Rd, although the original has long since been replaced.) You can watch Nigel's video here.
If you choose to visit this location you can also walk down East Heath Rd to Southend Green, as Smiley did. Le Carre, who had a house nearby and knew the area well, describes all this in the novel.