First Desk is the formidable, nameless head of the British intelligence service at Regent's Park. She is a master strategist who views politicians as temporary nuisances and prioritizes the autonomy and preservation of the Service above all else. Operating with a cold, pragmatic detachment, she uses her deep knowledge of bureaucratic loopholes and institutional machinery to thwart any external oversight.

Griselda is a seasoned Home Office administrator who serves as the first chair of the politically motivated Monochrome inquiry. Initially weary and financially strained due to her ex-husband's debts, she acts as a passive civil servant trying to protect her job. However, her deep frustration with institutional inertia pushes her to seek a genuine sense of purpose when a mysterious file surfaces.

Max is a retired academic living a peaceful, solitary life in the countryside, filling his days with long walks and Dickens novels. This gentle facade abruptly shatters when assassins attack his home, forcing him to rely on dormant, lethal survival skills. He is a resourceful and capable man whose carefully constructed retirement masks a dangerous history tied to the intelligence services.

Molly is the archivist at Regent's Park and a woman who uses a wheelchair due to a traumatic injury from her past. As a junior officer operating under the name Alison North in the 1990s, she is thrust into the morally ambiguous and chaotic world of post-reunification Berlin. In the present, she is a composed and strategic operator who uses her mastery of the archives to assert influence.

Malcolm is an ambitious but insecure junior civil servant acting as the second chair of the Monochrome inquiry. Desperate for approval within the Whitehall system, he is initially focused on protocol and career advancement. When his professional prospects collapse and a classified document mysteriously lands in his shopping cart, he is forced to decide between following the rules and seizing control of his fate.

Brinsley is a brilliant and deeply cynical spymaster stationed in Berlin during the 1990s. He prioritizes on-the-ground instincts over official protocol, spending his time in bars and underground clubs to gather intelligence. Harboring intense guilt over a past operational failure, he is willing to run off-the-books missions and manipulate those around him to achieve his goals.

Fabian is an affluent and influential businessman attempting to secure a lucrative privatization contract for the UK's vetting services. His polished, corporate exterior hides a ruthless and violent past operating in divided Germany. He represents a modern evolution of power, using wealth and data control to achieve the kind of dominance he once sought through espionage.

David is a legendary and highly influential senior spymaster at Regent's Park during the 1990s. He is a master manipulator who views agents and assets merely as pieces in a larger, deadlier game. He represents the deep-seated duplicity at the core of the intelligence service, perfectly willing to sabotage his own operatives to gain political leverage.

Carl is the CEO of Singer Industries and a wealthy entrepreneur with strong political connections. He serves as a member of the Monochrome inquiry panel while simultaneously positioning himself as the frontrunner for a privatized government vetting contract. He embodies the modern intersection of corporate power and state security.

Shelley is an intelligence operative currently on medical leave, claiming a leg injury as she awaits a payout before the service privatizes. She previously served as a welfare officer and handler for retired assets. She is cynical about the government's cost-cutting measures and fiercely protective of her own interests, though she retains practical field skills.

Anthony is a special adviser to the Prime Minister who acts as the political architect behind the Monochrome inquiry. He uses his position to weaponize government mechanisms for personal vendettas, embodying the cynical and self-serving nature of contemporary politics.

John is a current handler for retired intelligence assets, taking over duties that previously belonged to Shelley. He struggles with alcohol addiction, which leaves him vulnerable to operational security breaches.

Erin is a junior analyst at Regent's Park who previously served as First Desk's assistant. She is dedicated to her work but expresses growing disillusionment with the internal political battles that plague the intelligence service.

Janet is the Deputy Manager and Malcolm's former superior in the civil service. She is a pragmatic bureaucrat who advises Malcolm to avoid trouble and follow protocol, representing the rigid, self-preserving nature of their department.

Robin is the station chief in Berlin during the chaotic post-Cold War era. He struggles to maintain order in a chaotic environment of espionage and provides crucial context about secret operational funds to visiting auditors.

Bogart is the code name for a former Stasi officer who worked as a British intelligence asset. Her brutal murder when her cover was blown serves as the catalyst for the off-the-books operations driving the historical narrative.

Charles is the former First Desk at Regent's Park during the 1990s. His presence looms over the historical narrative, representing the deep institutional secrets and betrayals that shape the intelligence service's history.