My wife was wondering the other day, could "dear Arthur," late of her Majesty's Royal Navy, possibly be the same Arthur as mentioned by Dutton in 'Dance of the Dead' "It's a bore old man. The Committee, they want a breakdown of everyone, you, me, Arthur, the Colonel everybody." Yes, 'Many Happy Returns' does precede 'Dance of the Dead' in the series, but not according to the library list of episodes, as originally it would have been the other way round. So fictionally speaking Mrs Butterworth's husband could have been the same Arthur, and people working for British Intelligence were selected from the Armed Forces.
I'll be seeing you