She was educated at the Grey Coat Hospital Church of England girls' school in Westminster[2] and the University of Kent.

[citation needed] Dunwoody trained in the National Health Service, and worked in London hospitals for nearly 15 years.

[2] Dunwoody was elected (under the name Tamsin Dunwoody-Kneafsey)[3] as Assembly Member for Preseli Pembrokeshire from 2003 to 2007.

She was selected as the Labour candidate at the Crewe and Nantwich by-election, held on 22 May 2008, which was triggered by the death of her mother.

[7] The last parliamentary by-election in which the Conservatives had gained a seat previously held by another party was in 1982, in Mitcham and Morden.