According to Donald, the 18th century Sebastian Fergus MacDonald's "one passion in life was the cultivation of the perfect begonia". The begonia was not introduced to Europe until the 1860s.
The last time Paul goes to find their guest he calls for him by saying "Liam", though by then he knows his real name (and he is not saying this, as he probably had a moment before among others, to keep it a secret since no one else was with him).