What Jonty did in Blue Lights runs from the night Gerry died to the day he left Blackthorn — the full list
He is not the man who pulled the trigger, and the show has never pretended otherwise. What it has done instead is keep a running account of the smaller decisions, which is the more damning document.
Inspector David "Jonty" Johnston, played by Jonathan Harden, ran Blackthorn station in series 1 and functioned as the PSNI's point of contact with MI5. Jonathan Harden is on the returning cast list for series 4, which premieres on BBC One on 29 September 2026 and builds its season around the murder trial for Gerry Cliff. Which makes the timeline worth having straight.
Series 1: the night, and the week after
- The operation — Jonty was working alongside MI5 on surveillance of the McIntyre organization. James McIntyre had been an MI5 informant since 1998, and MI5 pressed him to let his son Mo's arms deal with the Ginleys go through so the weapons could be tracked.
- The tip-off — Gerry Cliff, on information from his childhood friend Happy, drove into an out-of-bounds area and walked into the deal. A Dublin gunman shot him.
- The witnesses — two MI5 officers watched Gerry die and left the scene. When they were brought into Blackthorn, Jonty released them on a public interest immunity certificate rather than let them be interviewed.
- The room — Stevie lost his temper over it, which for Stevie is notable. Superintendent Nicola Robinson wanted to know why two witnesses to a constable's shooting had walked out of the station.
- The affair — separately, Jonty had been sleeping with fast-track probationer Jen Robinson, who was using the relationship to stay off frontline patrol, and who is Nicola Robinson's daughter. McNally found them together.
- The exit — Jen admitted what she'd been doing and left policing. Nicola Robinson forced Jonty's resignation.
The evidence that eventually closed the case came from Grace, not from him: MI5's own camera footage, showing the two officers watching the shooting and leaving, which was leverage enough to give up the McIntyres' location.
The immunity certificate is the act the show keeps returning to. Gerry's killer was caught. The two men who stood there were driven home.
Series 2: brought back for his contacts
Jonty returns in episode 2, "Iceberg," with no authority left and no enthusiasm for it. McNally has no intelligence assets on the Mount Eden estate, Jonty has years of contacts there, and she recruits him on the grounds that he owes the team.
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What he does with it:
- Episode 3, "Love Knows" — runs a neighborhood meeting where Lee Thompson confronts him publicly about police inaction on protection money. He follows up at The Loyal pub, where Mags orders him out. He reports back to McNally: "We've lost Mount Eden — maybe we lost it a long time ago."
- Episode 4, "The Stamp of Nature" — asks Aisling to verify a letter of Thompson's about community center funds, then puts the letter to Rab, who wrote it.
- Episode 5, "Where I Want to Be" — watching the footage of Gerry's death again with Tommy, he recognizes a face at the scene who is connected to Lee Thompson. "If they're working with Lee Thompson this is far worse than we thought." He sets Tommy to audit every police contact with Thompson in recent weeks and gives him access to a restricted section of the database.
- Episode 6, "The Loyal" — he works the doorbell footage and the Henry interview, and at the party afterward at the Orpheus, Sandra Cliff — Gerry's widow, and the station's custody sergeant — tells him she read his letter, and offers to buy him a drink.
The man who let two witnesses walk is the man who spotted the connection that reopened the file. The show declines to tidy that into a redemption.
What series 4 does with him
Harden is billed among the returning cast for series 4, alongside Richard Dormer in a special appearance as Gerry and Hannah McClean as Jen Robinson. The BBC's logline says the murder trial for Gerry Cliff drags a long-buried secret into the open.
For the record: Jonty appeared in all six episodes of series 1 and five of the six in series 2, and was absent from series 3 entirely. Three years of story separate his last scene from his next one.
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