Not just dad's Army, Neppy ...
....apologies for a little bit of thread drift. In Naples in the mid '80s there was PFC in the US Army southern region signals regiment who had been the CO until not long before I got there. I mentioned to my US Army colleague that I was slightly puzzled by the age of the PFC and the deference shown by the Capt who was his boss in the interminable meetings we used to have. He explained that the Colonel had come up to retirement age and asked if he could stay in service and in Naples. Not as a Colonel he was told. OK as what then?
PFC he was told. "I can live with that" he said and stayed. All the USN guys I worked with thought it was very odd and not entirely the done thing. Mind you they couldn't get their heads round Spec Aircrew either. "You mean you can go on flying till you're 55?"
The Ancient Mariner