The UK's decision to not join the Vietnam War was a complex one, rooted in the shifting dynamics of the Cold War and the evolving public sentiments of the time.

As the conflict escalated in Southeast Asia, the British government carefully weighed its strategic interests and the growing opposition to the war within its own borders.

At the heart of the UK's position was its delicate balance between maintaining its global influence and avoiding the potential quagmire of a prolonged military engagement.

Unlike the United States, which had a more direct strategic interest in the region, the UK's involvement in the Vietnam War was not seen as crucial to its national security. - https://vietnamfocusguide.com/blog/why-didnt-uk-join-vietnam-war/?unique_id_9h9jyhhd

"The UK's Neutral Stance: Examining Cold War Dynamics and Public Opinion on the Vietnam War"