From 1937, Hewitson was President of the International Trade Secretariat for the Public and Civil Service, a post which involved many visits to continental Europe where he became well known.
After the outbreak of the Second World War, Hewitson was one of the first national trade union leaders to leave some of his posts and volunteer to serve in the armed forces.
During the 1945 general election campaign on 29 June 1945, the sitting Labour MP for Kingston upon Hull Central Walter Windsor died.
He made a speech in his constituency in August 1952 insisting that differences of opinion within the Labour Party "did not require the existence of private and conspiratorial groups".
[7] In 1954, Hewitson "talked out" a Private Member's Bill introduced by Frederick Mulley which called for publication of football pools promoters' accounts.
Representing many fishermen, he moved a motion in Parliament to stop a proposed doubling in the levy for the White Fish Authority in September 1956.