They Knew Mr. Knight is a 1934 dramatic novel by the British writer Dorothy Whipple.

[1] Tom Blake, a factory worker, becomes involved with a shady financier known as Mr. Knight.

Guided by Knight, Blake becomes involved in series of bad investments and fraud.

The Times Literary Supplement wrote, "the portraits in the book are fired by Mrs Whipple's article of faith – the supreme importance of people"; while The Sunday Telegraph called the novel a "real treat.

"[2] The novel was adapted into a 1946 film of the same title directed by Norman Walker and starring Mervyn Johns, Joan Greenwood and Alfred Drayton.