|Title credit for the BBC adaptation
The mini-series length allowed the spycraft – where the smallest details are potentially significant, they accumulate and fit together, and those that don’t fit lead George Smiley to the traitor – to be set out in a slowly escalating, tense manner. It’s helped by Alec Guinness as George Smiley who plays it somewhere upstream from inscrutable as he works out the identity of the traitor. I had a look online and David Denby, who saw it in 2012, has written well about it in The New Yorker here
Tomas Alfredson’s adaptation has a couple of other telling, different details: a mother and child, or only a child (?) are caught in the crossfire of the first failed mission and George Smiley tells Peter Guillam, his assistant in tracking down the traitor, to get rid of anyone who might make him vulnerable. The next scene is Peter Guillam telling his male lover to leave without offering an explanation. These strike me as good, indicative details of the Le Carré world.