Gerald Seymour was born to William Kean Seymour and Rosalind Wade. He was educated at Kelly College at Tavistock in Devon and took a BA Hons degree in Modern History at University College London.
Initially a journalist, he joined ITN in 1963, covering such topics as the Great Train Robbery, Vietnam, Ireland, the Munich Olympics massacre, Germany's Red Army, Italy's Red Brigades and Palestinian militant groups. His first book, Harry's Game, was published in 1975, and Seymour then became a full-time novelist, living in the West Country. In 1999, he featured in the Oscar-winning television film, One Day in September, which portrayed the Munich Olympics massacre. He has been a full-time writer since 1978.
- Harry's Game (1975), ISBN 0-00-221866-6
- A British cabinet minister is gunned down by an IRA assassin, leaving an undercover agent to track down the killer.
- The Glory Boys (1976), ISBN 0-00-222399-6
- An Arab terrorist, the only survivor of a three-man hit squad ambushed by Israeli Intelligence in France, plans to murder Israel's leading nuclear scientist on a visit to London. McCoy, an IRA mercenary, is to provide him with the weapons. Jimmy, who works for British Intelligence, must find them. It was made into a 3 part TV mini-series in 1984 by Yorkshire Television, starring Rod Steiger, Anthony Perkins, Alfred Burke and Joanna Lumley.
- Kingfisher (1977), ISBN 0-00-222353-8
- A story of three Soviet dissidents, Ukrainian Jews, who hijack a plane to escape to the West. They land in England but it is not certain how they will be treated – as political refugees or murderous criminals?
- Red Fox (1979), ISBN 0-00-221444-X, published in the U.S. as The Harrison Affair
- When Italy's most ruthless terrorist is captured, her lover uses a British businessman, who has been kidnapped in Rome, as a bargaining tool to free her and unleashes forces which threaten to escape everyone's control. It was made into a TV mini-series in 1991, starring John Hurt, Jane Birkin and Brian Cox, but reset in France with the terrorists members of Action directe.
- The Contract (1980), ISBN 0-00-221998-0
- Set against a backdrop of the treacherous East/West German border, this tells of the journey to redemption of a disgraced British army officer who requires the defection of a top flight Soviet scientist.
- Archangel (1982), ISBN 0-00-222621-9
- Running a small errand for the British Intelligence Service turns into a nightmare for a young man when he is arrested by the Soviet Secret Police and sentenced to 15 years in a desolate labour camp.
- In Honour Bound (1984), ISBN 0-00-222764-9
- Barney Crispin, SAS captain, is sent urgently to the Afghanistan border on the direct order of the Foreign Secretary. His mission is to organize the destruction of one of the new Soviet helicopters and to bring its secret parts back to Britain.
- Field of Blood (1985), ISBN 0-00-222870-X
- Two men, one ex-IRA, the other a reluctant British Lieutenant, become pawns in a deadly political game of cat-and-mouse.
- A Song in the Morning (1986), ISBN 0-00-223106-9, published in the U.S. as Shadow on the Sun
- Jeez Curwen, a British undercover agent, is captured taking part in a terrorist attack in apartheid-era South Africa. By the time his son Jack discovers that the British government has washed its hands of his father's case, Jeez has only three weeks to live. Aided by the ANC, Jack decides to free him.
- At Close Quarters (1987), ISBN 0-00-271013-7, published in the U.S. as An Eye for an Eye
- A diplomat and an Israeli master sniper plan to walk by night into the Beqa'a valley in east Lebanon, home of Palestinian revolutionary groups, in search of one man. They are far into the Beqa'a, out of reach, when their cover is blown and Syrian Intelligence alerted to their approach.
- Home Run (1989), ISBN 0-00-271018-8, published in the U.S. as The Running Target
- Mattie Furniss is ordered to Iran by British Intelligence to fortify his remaining agents and stimulate a flow of information. Unknown to him, Mattie's mission is about to be blown wide open by political pressures, and he is soon left alone in a hostile environment where his every move is tracked.
- Condition Black (1991), ISBN 0-00-271176-1
- A thriller set against the background of Saddam Hussein's annexation of Kuwait and his efforts to arm Iraq with nuclear weapons. An attempt to recruit a British nuclear scientist falls foul of an FBI man's vendetta against a British terrorist who killed his best friend.
- The Journeyman Tailor (1992), ISBN 0-00-271233-4
- Gary Brennard is young and keen, just the qualities his MI5 desk chief seeks for an undercover operation in Northern Ireland. There is a suspicion that an informer is among the villagers of County Tyrone.
- The Fighting Man (1993), ISBN 0-00-224305-9
- Thrown out of the SAS, Gord Brown is working on a fish farm in Scotland when he is found by Central American Indians on a mission to recruit a "fighting man" for an uprising against the Guatemalan military dictatorship. Gord joins up as deputy leader of the rag-tag group in this adventure thriller.
- The Heart of Danger (1995), ISBN 0-00-225009-8
- The international community had promised it would hunt down the war criminals of Yugoslavia, but when the body of a young Englishwoman is exhumed from a mass grave in Croatia, her mother cries for justice and is ignored. Private investigator Bill Penn takes on the case.
- Killing Ground (1997), ISBN 0-593-04098-8
- A young English schoolteacher, Charlotte Parsons, is invited to resume her job as nanny to the children of a well-to-do Sicilian family. But this time Charley is the central figure in a desperate plot by the US Drug Enforcement Agency to trap Mario Ruggerio, would-be head of the Sicilian Mafia.
- The Waiting Time (1998), ISBN 0-593-04211-5, published in the U.S. as Dead Ground
- On a winter's night at the height of the Cold War, in a small town on the Baltic coast of East Germany, a young man is dragged from the sea and killed by the regime's secret police. The witnesses are terrorized into silence. A decade later the man's lover sets out to attain justice.
- A Line in the Sand (1999), ISBN 0-593-04459-2
- In a village on the Suffolk coast, Frank Perry waits for his past to arrive. A decade ago, he spied for the government on the Iranian chemical and biological weapons installations. Now Iran has despatched its most lethal assassin to take revenge. Can Perry's protectors stop him?
- Holding the Zero (2000), ISBN 0-593-04425-8
- A suspense novel set against the backdrop of the Gulf War, where two of the world's greatest snipers fight a duel in the hills of northern Iraq.
- The Untouchable (2001), ISBN 0-593-04650-1
- Albert Packer is master of all he surveys. He rules the manor with an iron fist. For 20 years, he has had it all his own way – the police and intelligence services have targeted him but have yet to get close to any sort of effective prosecution.
- Traitor's Kiss (2003), ISBN 0-593-05091-6
- Officially the Cold War is over. Between former enemies, the hand of friendship is exchanged in public. In private, though, the intelligence war goes on.
- The Unknown Soldier (2004), ISBN 0-593-05258-7
- Hidden in the empty vastness of the world’s greatest desert a tiny caravan of fugitives and camels moves painfully slowly towards its goal. Above them, quartering the desert, is the unmanned Predator aircraft that is invisible in the cloudless skies and that carries Hellfire missiles.
- Rat Run (2005), ISBN 0-593-05508-X
- When word spreads that Military Intelligence officer Malachy Kitchen, posted to Iraq, was 'yellow' under hostile fire, his life starts to disintegrate. Kicked out of the army, he becomes an isolated recluse on a drugs-infested London estate. But the mugging of an elderly widow draws him to regain his lost pride.
- The Walking Dead (2007), ISBN 978-0-593-05754-4
- A young man starts a journey from a village in Saudi Arabia. He believes his life will end in faraway England. There, David Banks is a Metropolitan Police armed protection office charged with neutralizing the terrorist threat. On a spring morning in a suburban town these two men's paths will cross. Before then their commitment will be shaken by the journeys that take them there.
- Time Bomb (2008) ISBN 978-0-593-06005-6
- Fired from a top-secret Soviet nuclear base a Russian KGB officer steals a suitcase bomb - a tactical nuclear weapon. Fifteen years later, still harboring resentment over being discarded and abandoned, the Russian aims to sell it to the highest bidder - the Russian Mafia. Against them a small and dedicated MI6 team and a Metropolitan Police undercover man. With the clock ticking down to the handover the MI6 team must find the Russian Mafia gang and their undercover man and stop the sale of the bomb. The novel attracts interest on a number of levels. Firstly, it presents graphic descriptions of Nazi brutality. It is this brutality that shaped willingness of a man two generations later to participate in this scheme, even though he had no need for the large sum he would obtain through brokering the transaction. Further, it describes the undercover man, and his exposure to events conducive to the "Stockholm Syndrome."
- The Collaborator (2009) ISBN 978-0-340-91886-9
- The prime reason Immacolata Borelli came to Britain was to look after her gangster brother, wanted for multiple murders back home in Naples. The Borelli clan are major players in the Camorra, and they will not lose their criminal empire without a vicious fight. They will use any tactic and any person in a brutal struggle to keep control of their territory in the city, and to prevent her from giving evidence against them. This novel throws a stunning light into the dark world of the Camorra.
- The Dealer and the Dead (2010) ISBN 0-340-91890-X
- Eighteen years after the barbarous war with the Serbs that tore their communities apart, a group of Croatian villagers discover the identity of the Englishman who they believe betrayed them by welching on a deal to supply arms. With revenge in sight at last, they hire a professional killer from London to track him down ...but is the story as simple as they think? A brilliant, bruising thriller, told in a unique way, about what happens when the hand of the past suddenly reaches out to the present - and is holding a gun. Benjamin Cumberland Arbuthnot (Benjie) and his wife Deidre are significant to the story. He is a retired senior SIS officer.
- A Deniable Death (2011) ISBN 978-1-4447-0586-7
- "Two British operatives, known as Badger and Foxy, experts in covert surveillance, are sent to the Iran-Iraq border to watch the house of a man they call the Engineer for his deadly, expert combinations of high explosives and circuit boards that are causing havoc among NATO troops in Iraq. The tradecraft of silent watching and the discomfort, thirst and increasing claustrophobia of the hideout are brought ... to life.... [As is] the grim landscape of the border region and the harsh lives of its inhabitants...: the flat plains and marshes..., the minefields and burned-out tanks still rusting from the Iran-Iraq war of the 1980s, the wretched locals who make a living, and dying, by digging up ordnance and selling it for scrap. [The Engineer] believes himself a soldier at war and a patriot, just as his victims do. His wife Naghmeh, a doughty activist demanding that the minefields be cleared, is suffering from a terminal brain tumour and needs urgent medical treatment in the West. Death duly comes, but to more places than expected."
- The Outsiders (2012) ISBN 978-1-444-70588-1
- "Winnie Monks, known as 'the Boss', is in charge of the Organised Crime Group. When one of the team is kicked to death and his hand severed, Winnie vows she will bring his killer to justice. Years pass, and government cuts reduce her team. But she learns that the killer is 'the Major', a Russian gangster en route to Marbella.... Winnie mounts an operation to bring about his destruction.... Winnie is a forceful creation, with her burning resentment against those who feel contempt for the way the rest of us live. 'They are so arrogant, those people,' she mutters. 'They think they're untouchable.'"
- RLK! Spotlight On
- "Summer Thriller: Human engineering", The Economist, 13 August 2011.
- "The Outsiders, By Gerald Seymour", Barry Forshaw, The Independent, 27 August 2012.