You want the short version. Okay, then: shit happens. Does that answer all your question? Thought not. Now, if you shut your face and let me tell thi… - Tom Holt

The knight raises both eyebrows, like someone by Burne-Jones who's just trodden on something sharp. 'I am Prince Boamund, eldest son of King -'
'Boamund?'
'That's right,' says the knight, 'Boamund, eldest son of -'
'How do you spell that?'
Boamund looks worried. Where he comes from you can take advanced falconry, or you can take spelling; not both. Guess which one he opted for. - c. 1

You twist everything," he said.
"Guilty," I said. "Though I prefer to think of it as a form of art.

It’s a basic tenet of military science. No stronghold can be taken if a mule laden with gold bars can leave it unobserved.