Canaris's escape route through Plymouth

How could Canaris plausibly have passed through Plymouth on his escape from Chile?

He may have stayed aboard ship, relied on friends among the crew, and avoided going ashore, which was the behaviour British authorities would have expected from a spy.

A viewer finds Canaris's route from South America to Germany difficult to credit. He was a capable and complicated intelligence officer, but the gaps in his journey do not by themselves prove the existence of a complete secret network. Britain had limited reach in Chile, and few people expected a fugitive to choose this route. Friends among the crew and a refusal to go ashore could therefore have made his passage through Plymouth less conspicuous than it sounds.