The final episode to feature Private Cheeseman, the character intended to be a replacement for Joe Walker (the late James Beck.) John Laurie objected to the character and as such he never returned.
Godfrey says he sang a song about a monk and Pike says it was about a monk of high renown. There is a song called Monk of Great Renown which can be traced back to the 1890s but it's lyrics are extremely un-Godfrey-like.