The toruble is you then have to invent the ludicrous deadlock seal(tm) to stop him if needs be
I have less problem with opening doors then locking them, sometimes the key in the door is just easier!
One of my favorite gags in Smith and Jones was after the Doctor burned out his screwdriver, he and Martha flee into a room, the Doctor turns back to the door. The camera cuts to a closeup of the lock, and it's simply the Doctor's hand turning the knob on the lock. But the closeup is exactly the thing the show would do if he still had his screwdriver! It really emphasized the sense of "This will have to do."