Guy practised as a barrister and King’s Counsel in London for thirty years, dealing with cases featuring drug-taking cyclists, dead Formula 1 champions and aspiring cemetery owners. He now writes full-time.

His debut novel, Five Minds, is about five people sharing one body, one of whom is trying to murder the others. It was a Financial Times Book of the Year and a Kindle Number 1 Bestseller in Technothrillers and Post-Apocalyptic SF. Translation rights were sold in eight territories. 

His second novel, Black Lake Manor, is a locked room murder mystery set on Vancouver Island, with a killer who can unwind time. It was a Financial Times SF Book of the Month and a Waterstones Best Crime Book of 2022. 

For his third novel, A Trial in Three Acts, he has returned to the law, with a murder trial set in the Old Bailey.

When not writing Guy can usually be found running in the Surrey Hills; or writing mildly amusing letters to The Times.

He has appeared on the radio and podcasts; on panels at numerous literary crime festivals, including Harrogate, Bloody Scotland, Bay Tales and Crimefest; and at the SF Worldcons of 2023 (Chengdu) and 2025 (Seattle). Selected articles/interviews and podcast appearances are linked below.