Complete cast breakdown of Blue Lights season 3: Who plays whom & where you’ve seen them before

Blue Lights season 3 brings back its core PSNI officers while introducing new faces who deepen the show’s intense, character-driven world. The series continues to follow Grace, Annie, and Tommy as they navigate the demands of frontline policing in Belfast, balancing personal struggles with high-pressure cases.

Returning cast members include Siân Brooke, Martin McCann, Katherine Devlin, Nathan Branif, and Joanne Crawford, each reprising their established roles within the station. They are joined by familiar season 2 additions such as Frank Blake and Dearbháile McKinney. Season 3 also expands its universe with newcomers Cathy Tyson and Michael Smiley.

All cast members of Blue Lights season 3

Siân Brooke as Grace Ellis

Grace returns as a seasoned constable still shaped by her past as a social worker. This season, she faces emotional challenges when a figure from her history resurfaces and her relationship with Stevie becomes more complicated. Siân Brooke is known for major roles in Sherlock, House of the Dragon, and Good Omens.

In an interview with PrecinctTV on November 19, 2025, Brooke said this about the character,

"I’ve really loved the development of this character as an actor. The stuff she reveals about herself in season 3 is something that we’ve known about and sort of carried before we even started filming season 1. It’s informed everything she does and her responses. All the times Stevie said kids in care, she’s always, in her response, been like ‘you can’t say that.’ It’s really nice to tell her story in this way, and to give the reason why she is trying to make things better for people."

Martin McCann as Stevie Neil

Stevie steps into his new role as Sergeant while trying to stabilize his relationship with Grace. He also confronts added pressures within the team as investigations intensify. Martin McCann has appeared in Marcella, Vera, The Fall, and films such as ’71 and Clash of the Titans. 

Katherine Devlin as Annie Conlon

Annie continues her duties as a frontline officer while dealing with personal difficulties and the risks of everyday policing. Her close ties with Tommy and Shane shape much of her journey. Katherine Devlin earned attention through The Dig and has also appeared in Vikings. Blue Lights is her breakout TV role, marking her rise as a strong performer in character-driven drama.

Nathan Braniff as Tommy Foster

Tommy returns as a dedicated constable navigating a strained relationship with Aisling while sharing a home with Annie. A traumatic incident pushes him into difficult emotional territory. Nathan Braniff makes his on-screen debut with Blue Lights. His portrayal of Tommy has been praised for authenticity and depth.

Joanne Crawford as Helen McNally

Helen leads the team as Inspector, facing increased responsibility and a personal test when a former mentor arrives seeking help. Her decisions shape major case developments this season. Joanne Crawford is recognized for roles in Line of Duty, The Fall, and Chosen. She has a long career in Irish television and theatre, often portraying authoritative and grounded characters.

Andi Osho as Sandra Cliff

Sandra steps into her promoted role as section skipper after her husband Gerry’s death. This season sees her work closely with Stevie and manage rising station pressures. Andi Osho is known for Good Omens, Sex Education, I May Destroy You, and Stay Close. Apart from acting, she has a background in stand-up comedy and writing, giving her a diverse creative profile.

Frank Blake as Shane Bradley

Shane continues as Annie’s partner, with their romantic connection developing alongside the dangers of the job. He remains central to several high-risk cases. Frank Blake is widely recognized for Normal People, Sanditon, Blackshore, and appearances in Vikings: Valhalla and Bridgerton. His work spans period drama and contemporary thrillers.

Dearbháile McKinney as Aisling Byrne

Aisling’s relationship with Tommy deepens, but a traumatic event leaves her emotionally vulnerable. Her storyline explores the psychological impact of policing. Dearbháile McKinney has appeared in Derry Girls, Malpractice, and Fate: The Winx Saga. Her growing body of work highlights her as an emerging talent in Irish drama.

Michael Smiley as Paul ‘Colly’ Collins

Colly arrives as Helen’s former mentor, now involved in intelligence work. He pulls Helen into a complex investigation involving organized crime. Michael Smiley is known for Luther, Bad Sisters, Black Mirror and films like The Lobster and Free Fire. His career spans decades, marked by distinctive and dynamic performances.

Cathy Tyson as Dana Morgan

Dana runs an exclusive Belfast members club but hides deeper ties to the criminal world. Her storyline reveals vulnerability under a tough exterior. Cathy Tyson is acclaimed for Mona Lisa, earning BAFTA and Golden Globe nominations. She has recently starred in Boiling Point, Criminal Record, and Dune: Prophecy, maintaining a long, varied career in film and television.

Catch Blue Lights season 3 on BBC One.