In re-tracing the General's movements it is said that as he used his stick in his left hand his left leg must have been the lame one. In fact it is more normal to use the walking aid on the opposite side to the afflicted limb.
In his darkroom, Smiley makes two mistakes with the 35mm film frame he has found. first, he makes a contact print of it, yet he doesn't bother to cut a piece of from a sheet of photographic paper but wastes an entire sheet. He then examines the print under a magnifying glass, as the image is only 36x24mm. But he must have an enlarger in the darkroom, so why didn't he make a full-size print instead?