[7] He was also the director of programmes for Radio Free Scotland[8] from 1963 to 1965, and was Senior vice-chairman (depute leader) of the SNP from 1970 to 1972,.
[2] He was selected as the SNP candidate for East Aberdeenshire in 1972, and moved to live in the constituency, developing links with local fishermen, farmers and businessmen.
[7] Henderson served as the whip and was a leading member of the group of 11 SNP MPs in the House of Commons.
In 1975, he negotiated a position for the SNP's Winnie Ewing in the British delegation to the European Parliament,[4] where she became known as "Madame Ecosse".
He was instrumental in the SNP's decision to lay down a censure motion in the House of Commons, criticising the Labour government of James Callaghan after 1 March 1979 referendum vote on Scottish devolution failed to be approved by the required 40% of the electorate.
The motion was carried by one vote on 28 March and Callaghan immediately called the general election which brought the Conservative Party led by Margaret Thatcher to power.
[7] Henderson lost his seat to Conservative Albert McQuarrie in the 1979 general election by less than 600 votes, and only two MPs from the SNP remained in the new Parliament.
He was selected to fight the Falkirk East constituency for the 2007 Scottish Parliament election, and was ranked fourth on the SNP's Central Scotland regional list.