What is the plural of "detective sergeant". In an episode of *[Endeavour][1]*, 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.


  [1]: https://www.springfieldspringfield.co.uk/view_episode_scripts.php?tv-show=endeavour-2013&episode=s05e04