Mitford was educated at Milton Abbey and Highgate School, before going up to Newcastle University, where he graduated with the degree of BA.

[3] By convention, the House of Lords refer to peers holding multiple titles by whichever is senior within the peerage.

He has spoken on various issues on behalf of the Liberal Democrats Parliamentary Party, such as the environment, international development, and science and technology.

[9] In November 2013, he, along with Jason Franks (formerly of the Daily Mail and General Trust events division), founded Heelec, which launched the Energy Management Exhibition (EMEX).

The amended bill—the Ecology Bill—passed through its remaining Lords stages successfully, and was handed over to Wera Hobhouse (Liberal Democrat MP for Bath) on 25 April 2023.

He lives with his wife, Helen (née Shipsey), Lady Redesdale, who is a lawyer, and their four children (Bertram, Clementine, Amelia, Edward) near Tufnell Park, north London, as well as in Northumberland.