I finally found something that is new to me and I like it. Aw yiss.
"Sexuality was a very powerful tool then. I keep my character’s homosexuality secret because you are so open to blackmail. It necessitates a certain amount of secretiveness, which goes hand in hand with spying. We talked about the idea that Guillam would have been a frozen child at one of the military public schools and there would be a distance between him and his parents, partly because of the work he was involved in. Guillam is in love with a man who’s older than him, and Smiley is another sort of father figure." x
Benedict Cumberbatch in Tinker Tailor Soldier Spy (2011)