Not totally on message (am I ever) but this triggered me to check point I had noted on IMDb listings before. For Ken Kitson's appearances he gets listed variously as 'PC Cooper', '1st PC', 'Policeman (uncredited)' in 'The General's Greatest Battle', 'Policeman', '1st Policeman', 'PC
#1 ', 'Police Constable'
AND, and this is specifically what I was wanting to recheck:
'2nd P.C.' in 'Support Your Local Skydiver' and 'There Goes the Groom'
'2nd Policeman' in 'Stop That Bath'
'the Second Policeman' in 'Stop That Castle!'
'Second Policeman' in 'Happy Birthday, Howard'
In other words, he was mostly, but not always, First Policeman.
I do just have vague memories of seeing Tony Capstick at the wheel.