Holt led the SDP to a landslide election victory in 1945.
The Holt government was one of the most radical and reforming in English history, nationalising key sectors of the economy, inluding the railways, steel and coal industries. Holt also built an expansive welfare state, including universal health insurance, universal pensions and unemployment benefit.
Following the defeat of 1951 Holt continued to lead the SDP in opposition, before retiring aged 75 in 1955. He remained a backbench member of parliament until his death in 1967.