Harold Minchum was Minister for Magic from 1975 to 1980. He reinforced Azkaban with more dementors, but was still unable to stop Voldemort’s rise to power. (Pm)
Mila L. notes:
The name "Harold Minchum" is a near-homophone of Harold Wilson, Prime Minister of the United Kingdom whose second term in office (1974 to 1976) would have coincided with that of Harold Minchum's.
Minchum's tenure as Minister would have been at the same time as muggle Prime Minister James Callaghan, including a slight overlap with Harold Wilson and Margaret Thatcher.