Security guard (They Shall Not Pass)

A security guard prevented people without their pass from entering the BBC Television Centre. On the basis of this strict application of policy, he refused entry to a cast member claiming to work on Doctor Who, with the guard insisting that anyone could make such a claim. What the guard was, for some reason, failing to take into account was that the cast member was a live Zygon. (NOTVALID: They Shall Not Pass)