Reg Prentice

Formal switch from cabinet. Prentice served in Harold Wilson's cabinet, was deselected by left-wing activists in his Newham North East constituency, and crossed the floor to the Conservatives in 1977, the most senior Labour figure to do so. He won Daventry for the Conservatives in 1979 and served as a minister under Thatcher. His case became a touchstone in the Labour arguments over mandatory reselection that helped drive the SDP split.