Seabrook was born in London on December 14, 1930. He was educated at the London School of Economics, where he studied sociology and history. After graduation, he worked as a journalist and broadcaster for several outlets, including the BBC, The Guardian, and the Daily Mirror.
In addition to "The Unholy Alliance," Seabrook wrote extensively about British politics, international relations, and social issues. Some of his other works include:
- "The Race into Politics: The Changing Character of British Political Life" (1968)
- "The New Right" (1970)
- "Working-Class Conservatives: A Study in Political Sociology" (1977)
- "Beyond the New Right" (1984)
- "Thinker B: the Spy Within" (1994)
- "The Right's Revolt: The Tory Road to Revolution" (1995)
- "The New Penguin State of Britain: The 21st Century Guide" (2002)
- "A Life of Contradictions" (2009) (memoir)
Throughout his career, Seabrook was a vocal advocate for social justice, and he was known for his critical analysis of both left- and right-wing politics. He passed away on October 12, 2009, at the age of 78.