During the mid-1950s, when Lawson was preparing his famous paper, fusion research was highly classified. Though he completed the calculation in 1955, at the urging of his boss John D. Cockroft, he presented the paper in September 1957 at the British Association for the Advancement of Science Meeting. Lawson once noted, "It was the first time that anything was said about fusion in public. Zeta and other experiments were classified, but my criterion was not, so it was allowed to be talked about." Fusion was declassified the next year throughout the world at the Second United Nations Conference on the Peaceful Uses of Atomic Energy.
Lawson was an engineer. He once said, "I had wanted to do physics, but they wouldn't take me because I hadn't done chemistry in grammar school. So I took mechanical sciences, which is an engineering degree. For that reason I was somewhat different from most people who had been educated in straight physics. And I think in a slightly different way."
Lawson worked on the development of microwave technology during the Second World War. In 1951 he joined a group led by Peter Thonemann, sometimes called the father of the U.K. fusion effort. Lawson said it was Thonemann who got him interested in fusion, saying, "Thonemann was so enthusiastic and so unrealistic that I thought I'd like to pin it down. So I wrote the paper."
Though Lawson had a lasting and fundamental impact on fusion research, he spent the bulk of his career working in the field of charge particle beams, and wrote the classic textbook, "The Physics of Charged Particle Beams."
He retired in 1987 and was 84 when he died. In 1983, he was named a Fellow of the Royal Society "for his contributions to the field of applied electromagnetism, in particular the physics of charged particle beams and high temperature plasmas."