There are 11 episodes, from the first two series, for which there are no known copies in existence, although full unedited studio recordings do exist for The Worst Soldier I Ever Saw (1969) and an off-air soundtrack for Once a Big Man, Always a Big Man (1969) was recovered in 2019.
The swinging lightbulb in the opening titles was not merely some attractive credit sequence design: The Section regularly made use of a 500 watt lightbulb swinging in the face of interrogation suspects to help disorientate and frighten them.
The series theme tune was 'Girl in the Dark', a stock library track by Jack Trombey published by de Wolfe Music. In 1970 Edward Woodward released a vocal cover of the piece, 'This Man Alone', with lyrics by Peter Dacre.
Peter Bowles played Toby Meres in A Magnum for Schneider (1967) - which was effectively the series pilot - but was unavailable to record the full first run. Jeremy Lloyd was an early choice to replace him, before Anthony Valentine was cast.
The Section used a series of colour-coded files. A Red File was for especially dangerous targets of most urgent priority, marked for death. A Yellow File indicated a subject under occasional surveillance. Blue Files were for members of the 'wrong' party. White Files were for people who were to be put out of action by sending them into divorce courts, bankruptcy, prison or mental homes.