Letter from Countess
The letter from the Countess to Von Papen, read by the Germans in Istanbul, exposing Mason as a "British Agent:" this goes by so fast, but what is her motivation? We knew she'd written to Tayler, the British ambassador, exposing him as the source of the leaked documents. So why write to Von Papen?
Perhaps it's just a plot device to lend credence to von Richter's thorough discounting the plans for D-Day, ripping them to shreds. But it's plausible the Countess was playing some double game.
If anyone has a clearer understanding, would appreciate their sharing it.