In The Imitation Game (2014), why did Menzies tell Turing that his fiancée is in jail? Turing said something, and the guy said she's not in jail, she's out shopping. What was the information that Turing gave? Was it a blackmail because he was gay?
Menzies wanted to tie Alan to himself to help him decide which secrets to release to the Soviets. Lying about the only person that Alan cared about got Alan's stance much softer.
After that, Alan immediately admitted that he knew who the spy was (even though it was a certain way to get himself unwillingly "outed"), and he had no choice but to accept Menzies' "offer" after that, especially when Menzies practically told Alan that he knew that he was gay ("I know a lot of spies, Alan. You've got more secrets than the best of them.").
So, the point was to get Alan to do with the information for Soviets the same thing he did with the information for their own government.