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Um, the David werewolf wasn't captured. After killing the businessman, David has had his fill of human meat and goes somewhere to sleep it off, preferably in the company of similar animals. Somehow, he finds London Zoo and breaks into the wolf enclosure and curls off to sleep with them. That's why he's waking up in the morning, in human form and naked, and absolutely shocked to find himself there. He obviously has no memory of the night before.

What surprises me is how a huge werewolf could travel from the Underground station, across London, and find the zoo, when he's never been there before, without being seen or him attacking even more people. Well, it was nighttime, and probably early hours by then, and he was most likely feeling more full and sleepy than aggressive.

The above poster is correct. In addition, we do see the escalator victim again - as a corpse in limbo in the porn theatre. Sounds like you need to watch the film again, paying more attention.