2 of 2 added link, and short excerpt from script

What is the plural of “detective sergeant”?

What is the plural of "detective sergeant". In an episode of Endeavour, Series 5, episode 4, Superintendent Bright used "detectives sergeant" but this seems wrong, you wouldn't say "chiefs inspector" would you?

Chief Superintendent Bright, Thames Valley, Detectives Sergeant Strange and Morse, and Detective Constable Fancy.