S1·E5 Tinker Tailor

Smiley calls on ex-Circus spy San Collins, who was the duty officer the night Jim Prideaux was shot. Collins confirms the events as Smiley understands them and that Prideaux's good friend Bill Hayden is the senior officer who took charge of the case after all hell broke loose. Smiley subsequently meets with Prideaux to get a firsthand account of the events during the disastrous Operation Testify in Czechoslovakia.