A Circle of Deception?
It's I think a 50's world war II film. A British officer is sent to I believe France in possession of vital war info. He is given a suicide pill and told to take it if necessary and not let info fall into enemy hands. He is captured by Germans and either doesn't take or cyanide pill doesn't work. He is tortured and reveals info to Germans. Either he is rescued or at end of war it is revealed to him it was a deliberate plan to feed incorrect info to the Germans.
Spot on, as soon as I saw Bradford Dillman's name in cast list I knew you were correct it all came back to me.
You really have an encyclopedic knowledge.
It was actually released as Circle of Deception (no "a" on the beginning of the title) and starred Bradford Dillman; Suzy Parker and Ronald Allen. It was a black and white CinemaScope picture released by 20th Century-Fox.