The undercover policeman (Smedley) is a Detective Sergeant in the C.I.D. However, he appears at court in full uniform and helmet.
When Rumpole is in the taxi queue at the station, a group of people can be seen watching the filming.
Supposedly set in 1970, a 1977 model Ford Granada Mk2 is in the background as Rumpole boards a taxi at the railway station at 6 mins 45 seconds in.