When Smiley is playing the tape of the traitor's conversation back to the Circus leadership in the attic room, one can see through the small skylight, that it is daylight outside. Moments later the traitor is escorted to the waiting van, and it is nighttime again.
Lacon, Smiley and the other senior officers are having a meeting. They're seated around a table, Smiley immediately to Lacon's left. As Lacon speaks, he leans forward in his chair and puts his clasped hands on the table. In the next two shots of Smiley, Lacon's clasped hands can be seen in the lower left corner of the shot. Then Lacon leans back in the chair and takes his hands off the table, yet in the very next shot, Smiley is shown preparing to light a cigarette, and Lacon's clasped hands are still on the table in the lower left corner of the shot.