A chronological sequence of pocket diaries, larger hardback diaries and unbound typewritten pages of diary entries. Some of the latter are 'consolidated diaries' documenting some of the years in which Whittle worked on the jet engine. Those that are unbound are complete unless otherwise stated.

The diaries cover Whittle's professional activities such as work on the jet engine and the turbo-drill, and include details of meetings, telephone conversations and technical matters.