This article discusses the widespread opposition to the Vietnam war in Britain during the period 1964–1968. Focusing on the years of escalation, it covers the period when Lyndon Johnson occupied the White House and Labour Prime Minister, Harold Wilson, was in 10 Downing Street. Although Johnson was keen for a British troop deployment in South East Asia, Wilson steadfastly refused to provide one, although he did offer British diplomatic support to the war effort. Wilson often used his domestic situation, including dissent on the British support for the war, as a reason why he could not do more for the Americans. The article shows that, in the UK, there was never a majority in favour of US action in Vietnam and that the British public made their thoughts on the immorality and illegality of the war abundantly clear to those in high office in a variety of ways—from a consistent indication in the polls that Britain should not get involved militarily to impassioned and highly critical letters sent directly to President Johnson. © 2020, The Editor of the Journal.