Writing at pace

I am doing a lot of teaching on pace in fiction, which is so important. I have worked with several writers who create pace, who keep the story moving, then ruin it by putting in unnecessary detail, descriptions, back story etc.
The result is passages when the story starts to gather pace then we slow down again, which interrupts the narrative flow so that when we return to the story it’s like going from a standing start.  Such descriptions have their place but not when you are trying to keep things moving.
All books, but in particular thrillers and crime novels, rely on pace and the stop-start nature of some writing prevents the writer achieving it.
And yet with a few judicious cuts here and there, it is easily achieved.

John Dean