The Greatest Threat They’ve Ever Faced… Is The Truth. Grace, Tommy and Annie are back — but this time, a murder trial threatens to expose a long-buried secret shaking both the police and criminal underworld. With Richard Dormer returning as Gerry Cliff, explosive stunts and Tommy’s chaotic personal life, Blue Lights is heading into its darkest chapter yet.

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Blue Lights Season 4: BBC Confirms September Return for Hit Police Drama

The wait is almost over for Blue Lights fans. The BBC has confirmed that the acclaimed police drama will return this month, with Series 4 arriving on Tuesday, September 29, 2026.

The complete new season will be released as a box set on BBC iPlayer at 6am, while the first episode will also air on BBC One at 9pm that evening.

Set three years into the careers of response officers Grace Ellis, Tommy Foster and Annie Conlon, the fourth season will place the trio under mounting pressure as they face a new threat that the police are struggling to control.

Andi Osho as Sandra Cliff, Katherine Devlin as Annie Conlon, Siân Brooke as Grace Ellis, Nathan Braniff as Tommy Foster and Martin McCann as Stevie Neil in Blue Lights, walking through a corridor wearing police uniforms.

A Dangerous Secret Comes to Light

The new season will also revisit the fallout surrounding Gerry Cliff.

According to the official synopsis, the murder trial of Gerry Cliff will uncover a dangerous secret that has remained hidden for years. The revelation is set to create turmoil both within the police and across the criminal underworld.

As Grace, Tommy and Annie begin making important decisions about their futures, they will also have to confront what the series describes as the greatest threat they have faced so far: the truth.

The storyline promises to push the three officers beyond the pressures of their day-to-day work while bringing a deeper mystery into the centre of the drama.

Siân Brooke as Grace Ellis in Blue Lights, wearing a police uniform and stood in a street.

The Main Cast Returns

Series 4 brings back Siân Brooke as Grace Ellis, Martin McCann as Stevie Neil, Katherine Devlin as Annie Conlon and Nathan Braniff as Tommy Foster.

They are joined by Joanne Crawford as Chief Inspector Helen McNally, Andi Osho as Sandra Cliff, Frank Blake as Shane Bradley and Abigail McGibbon as Tina McIntyre.

Also returning are Dearbháile McKinney as Aisling Byrne, Neil Keery as Sergeant Lawrence McCloskey and Andrea Irvine as Chief Superintendent Nicola Robinson.

The new season will also feature Cathy Tyson as private members’ club owner Dana Morgan, Hannah McClean as solicitor Jen Robinson, Jonathan Harden as Inspector “Jonty” Johnston and Michael Smiley as C3 intelligence officer Paul “Colly” Collins.

Richard Dormer will make a special one-off return as Gerry Cliff, whose character was killed off in the first season.

BBC releases Blue Lights series 2 trailer and premiere date

What Can Fans Expect?

Nathan Braniff and Neil Keery have previously teased that the upcoming season could be the show’s strongest yet, with Braniff also revealing that viewers can expect plenty of large-scale action.

Speaking about Series 4, Braniff highlighted the stunts and pyrotechnics involved in the new episodes, while also describing Tommy’s personal storyline as chaotic.

The comments suggest that the new season will retain the elements that audiences have come to expect from Blue Lights while bringing plenty of action alongside its character-driven storylines.

The best TV in years”: the BBC's “BAFTA-worthy” crime drama Blue Lights is back with its most ambitious series yet

What Happens After Series 4?

There is also an element of uncertainty surrounding the show’s future beyond the upcoming season.

Series 3 and Series 4 were commissioned together, meaning the original renewal covers these two seasons. Once Series 4 has aired, the show’s future will therefore be less certain than it has been in recent years.

For now, though, fans have a new chapter to look forward to, with Grace, Tommy and Annie returning to the streets and a long-buried secret threatening to cause upheaval on both sides of the law.

Blue Lights Series 4 premieres Tuesday, September 29, 2026, with the full box set available on BBC iPlayer from 6am and the first episode airing on BBC One at 9pm.