What peculiar passenger did the British submarine HMS Trident transport during part of World War II?

During much of this time the submarine had a young reindeer doe on board. It had been presented as an unexpected gift by the Russians in August 1941 as part of the diplomatic ceremonies to honour the alliance between Russia and Britain. The Reindeer was named Pollyanna after the base and apparently adapted so well to life on board (being fed table scraps and condensed milk) to the point that she ate a few navigations maps. When the submarine returned to the UK Pollyanna had grown to the extent that the services of the local slaughterman had to be used to truss her securely so she could be safely removed from the boat. Pollyanna then proceeded to live out the rest of her days in the local zoo, bobbing her head three times whenever she heard a whistle, as was her military training.