Nationalist politician. Born in Edinburgh, Henderson was educated at the Royal High School and the University of Edinburgh, where he studied law. Having joined the Scottish National Party at the age of fourteen, he rose to become its Deputy Leader (1970-72 and 1979-81). He toiled behind the scenes to build the Party as a credible and electable political force, working within the prevailing system to achieve their aim of an independent Scotland. He used the illegal Radio Free Scotland to promote the cause and ensured that both candidates and election agents received training to maximise their chances of electoral success. This work paved the way for sensational victory achieved by Winnie Ewing in Hamilton in 1967.
Having worked hard to overcome the traditional Conservative dominance in North East Scotland, he served as Member of Parliament for Aberdeenshire East (1974-79). He was in the vanguard of the nationalist's electoral success in the 1970s and led the "football team" of eleven MPs who were elected to the Westminster Parliament at that time. He stood for election again both for Westminster and the European Parliament, but was unsuccessful. However, he was successful in business.
In his latter years he lived in Edinburgh's Lawnmarket and his funeral took place in St. Giles Cathedral. He is remembered as an intelligent politician, who was liked and respected not only by members of his own party but by his political opponents.