Q, I'm sorry to say that the only reference I have is the Oxford Book of Carols, which doesn't say when Mr Beard sang the carol to Watson, or when the Rev made the second transcription. Neither does it say how it came to the attention of the editors of the OBC, one of whom was Ralph Vaughan Williams.

If any the RVW Memorial Library at C# House holds any of his personal papers the answer might lie there.