Prior to full-time writing, Southwell worked as a journalist and as Director of Communications for the British Retail Consortium (BRC).
[citation needed] In his role at the BRC, he regularly clashed with the British government's media relations department and pressure groups, and played a part in forcing Stephen Byers to scrap the Rip-Off Britain campaign.
[citation needed] In a front-page story in The Sunday Times in 2003, Southwell, then a spokesman for the BRC, mentioned that MI5 was coordinating with the business community with regard to potential terrorism.
[citation needed] He has acknowledged a specialist knowledge and ongoing interest in the Angry Brigade and conspiracies surrounding the events that inspired VALIS.
A regular broadcaster in the UK and North America on the subjects of conspiracies and counter-culture, he jokingly claims on the back of his books that if he "dies a mysterious death it will be because he knows too much and has upset some very powerful people".