She'll star alongside Martin McCann, Richard Dormer, Katherine Devlin and newcomer Nathan Braniff.

Filming has begun in Belfast on Blue Lights, a six-part drama for BBC One, created and written by Declan Lawn and Adam Patterson who brought us The Salisbury Poisonings.
Blue Lights follows three rookie police officers working in Belfast, a uniquely dangerous place to be a police officer and is lead by Siân Brooke, Martin McCann, Richard Dormer, Katherine Devlin and newcomer Nathan Braniff with John Lynch, Jonathan Harden and Valene Kane also joining the cast.
Siân plays Grace, a mother of a teenage boy, has made the decision in her 40’s to leave her steady job as a social worker to join the Police Service of Northern Ireland. Having previously worked in social care she straddles a fine line between the personal and professional. It’s the biggest gamble of her life, and just a few weeks into the job, she’s making so many mistakes that her decision no longer looks like a winning bet.
Her fellow rookies are Annie, played by Katherine Devlin, who struggles with the fact that her chosen path may mean having to leave everything she’s ever known behind, and Tommy, played by Nathan Braniff, who is desperate to prove himself, despite being disastrously inept at the practical side of frontline response policing.
All three are new police officers in their probation period with the PSNI, the odds are at least one of them isn’t going to last. The pressure is immense, but if they succumb to it, they won’t survive.
Often the rookie officers don’t know the extent of the peril they are in, or who they can trust. What’s it like to have to hide your job from neighbours, friends and even family? How do you distinguish between who needs your help and who wants you dead simply because of the uniform you wear?
Speaking about playing Grace, Siân Brooke said "I am so thrilled to be playing Grace in Blue Lights. There is something incredibly special that Declan and Adam have crafted in these scripts and I was hooked from the very first page. Belfast is the beating heart of this piece and it’s a city I’ve been wanting to work in for a long time."
Writers and creators Declan Lawn and Adam Patterson said "Every writer wants to explore their own place, and their own society as authentically and as honestly as they can. We feel enormously grateful to BBC drama for letting us do that with Blue Lights. And to do it with a cast boasting so much new and established talent makes it even more exciting."
Inspired by extensive research and interviews, the series promises to be an authentic, gripping and darkly funny drama about ordinary people doing an extraordinary job in a society that could spiral out of control at any moment.
Executive Producer for Two Cities Television, Stephen Wright said "It is wonderful to have Blue Lights up and running in Belfast. We feel incredibly lucky to have this amazing cast on board along with the peerless crew in Belfast. With such great scripts from Declan Lawn, Adam Patterson and Fran Harris, and Gilles Bannier directing with passion and joy, we really couldn’t ask for more."
To which Louise Gallagher, Executive Producer for Gallagher Films added "Gallagher Films is proud and honoured to have worked with such a fabulous creative team to bring Blue Lights to life and we are so delighted that filming has now started. We can’t wait for viewers to see this unique and authentic story and extend our thanks to the BBC and Northern Ireland Screen for their unwavering support."
Made by Two Cities Television and produced with support from Northern Ireland Screen as part of their continued partnership with the BBC, Giles Bannier will direct, Carol Moorhead will produce and Fran Harris has written episode three and co-written episode four.
BBC's Drama Commissioning Editor, Tommy Bulfin said "Blue Lights explores a fascinating area we haven’t often seen before on TV and in a way that feels truly authentic. Declan and Adam have written it with such wit and heart that you instantly feel like you know our three rookies intimately. I’m so excited that filming has started in Belfast and look forward to seeing our excellent cast portray such brilliant characters."
Blue Lights will air on BBC One