Best Interests cast — who's who in the four-part drama?

Best Interests cast Sharon Horgan and Niamh Moriarty sitting on a bed together with a blue sparkly background.
Sharon Horgan and Niamh Moriarty star in the four-part drama. (Image credit: BBC)

Sharon Horgan and Michael Sheen lead the Best Interests cast, playing two parents battling to stop doctors from turning off the life-support machine of their disabled 13-year-old daughter. 

Created by Jack Thorne (National Treasure, Help) the powerful four-part series centers on Marnie, who suffers from a rare form of Congenital Muscular Dystrophy, a life-limiting condition that leaves her needing constant care. 

When her condition deteriorates, doctors believe it is in her best interests to be allowed to die, but her loving family disagrees. And so begins a fight that will take them through every stage of a legal process, as they struggle to contemplate this huge decision. Who decides? And in whose best interests will it be?

We take a look at the most important players in Best Interests... 

Sharon Horgan plays Nicci Lloyd

Sharon Horgan Best Interests

Sharon Horgan as Nicci Lloyd. (Image credit: BBC)

Nicci is Marnie’s mum and a warrior for her younger daughter. Nicci is naturally sparky and warm, while her long fight on behalf of Marnie’s interests has given her a steel too, forged from fighting other people’s doubts. Rocked by Marnie’s diagnosis, Nicci gave up her career — she was once the family’s main breadwinner — to care for Marnie. She has spent the intervening years struggling against downturns in Marnie’s health and overly pessimistic prognoses. Nicci’s closeness to Marnie gives her the faith to trust in a better outcome for her daughter this time too. 

What else has Sharon Horgan been in?

Sharon made her name in 2006 as the star and creator of BBC Three comedy Pulling and more recently won a BAFTA for hit C4 sitcom Catastrophe, which she wrote alongside co-star Rob Delaney. 

She has also written the award-winning BBC2 comedy Motherland and last year she starred in the first series of Apple+ show Bad Sisters. Her other TV credits include roles in Together, Divorce and This Way Up.

Michael Sheen plays Andrew Lloyd

Michael Sheen Best Interests

Michael Sheen as Andrew Lloyd. (Image credit: BBC)

Andrew is an easy-going guy who likes to put people at ease. He tries to enjoy life, despite the challenges his younger daughter, Marnie, faces every day. Andrew has traditionally taken on responsibility for keeping spirits up in the family, taking the sting out of a tough day. But the cheery mask he puts on can mean he doesn’t spend enough time with his own thoughts, fears, and worries; he pushes it all to the back of his brain. Andrew is also more feckless than Nicci, and that can be seen as a lack of care from time to time, despite his good intentions. 

What else has Michael Sheen been in? 

Michael Sheen is well-known for playing famous people and has starred as Tony Blair in The Queen, Brian Clough in The Damned United and David Frost in Frost/Nixon

His TV roles have included parts in acclaimed US period drama Masters of Sex, ITV series Quiz - in which he played Chris Tarrant - Amazon show Good Omens and recent C4 real life drama Vardy v Rooney: A Courtroom Drama

Alison Oliver plays Katie Lloyd

Alison Oliver Best Interests

Alison Oliver plays Katie Lloyd. (Image credit: BBC)

Katie is Nicci and Andrew's highly intelligent and independent eldest daughter. She’s older than her years, having had to take on the responsibility of looking after herself whilst her parents have cared for her younger sister. Although Katie has a maturity to her, there is also a slightly angry and rebellious side too, as we see her trying to cling on to a normal teenage life. As well as battling with the daily impact of her sister being unwell, Katie is also exploring her sexuality and hiding a secret relationship with Hannah. It is an exciting relationship, but a toxic one too, and could turn out to be destructive.

What else has Alison Oliver been in? 

The Irish actor is best known for her role as Frances Flynn in Hulu's Conversations With Friends. 

Niamh Moriarty plays Marnie Lloyd

Niamh Moriarty Best Interests

Niamh Moriarty as Marnie Lloyd. (Image credit: BBC)

Marnie is a warm, sharp-witted, and kind girl who has made the most out of her life. Marnie has a rare form of Congenital Muscular Dystrophy, and knows she may not live as long as everyone else. As much as that can upset and scare her, Marnie has found so many ways to enjoy her life and has defied expectations to live as long as she has. Marnie is strong like her mum, and has her dad’s sense of fun, but her most special bond is with her older sister, Katie.

What else has Niamh Moriarty been in? 

Niamh, who suffers from cerebral palsy, has played Tiny Tim in A Christmas Carol at The Gate Theatre in Dublin and had a role in short 2019 film My Mother's Shoes

Noma Dumezweni plays Samantha Woodham

Noma Dumezweni Best Interests

Noma Dumezweni plays Samantha Woodham. (Image credit: BBC)

Samantha is an intelligent, authoritative, and very experienced Consultant in PICU. She is also Marnie’s doctor, and a mother herself. Samantha acts with great care for her patients and that care is often demonstrated through making quick or tough decisions on their behalf. While she loses patients regularly — it’s par for the course with the extreme medical scenarios she encounters — and has dealt with many parents over the years, Marnie’s very public best interests case rocks her in ways she’s never experienced before as a doctor. 

What else has Noma Dumezweni been in? 

Noma Dumezweni has starred in a host of British shows, from Casualty to Doctor Who, before appearing in the hit US series The Undoing and The Watcher. She also plays The Queen in the remake of the Disney movie The Little Mermaid

Chizzy Akudolu plays Mercy Babayaro

Chizzy Akudolu Best Interests

Chizzy Akudolu as Marnie's nurse Mercy. (Image credit: BBC)

Mercy is Marnie’s nurse and a wonderful support to Marnie, and to the rest of the family. She is highly experienced, warm, and empathetic, and understands the pain that families go through. Mercy’s view of care is to put people at the heart of it all, not just look at the medical treatments and calculate outcomes. Although she always trusts the doctors’ expertise and would never seek to undermine them, we sense she does privately hold the view that parents could be listened to more and be a bigger part of the conversations around ending care. 

What else has Chizzy Akudolu been in?

Chizzy has played Mo Effanga in Holby City for several years and also appeared in cult ITV comedy Kate and Koji. Other screen appearances include being a contestant on Strictly Come Dancing in 2015 and on the panel of ITV1 chat show Loose Women

Lisa McGrillis plays Brenda Haskins

Laura McGrillis Best Interests

Lisa McGrillis plays Brenda Haskins. (Image credit: BBC)

Brenda is a charming, relatable, and persuasive person and it’s she who first encourages Nicci to go public with Marnie’s case and challenge the hospital’s decision in court. Brenda and her associates in Every Christian Life — a campaigning organisation — believe firmly in the sanctity of life and pour resources into fighting legal battles along those lines. But Brenda is canny enough not to be too vocal about her own deeply held Christian beliefs, which are more fervent than Eddie’s. 

What else has Lisa McGrillis been in? 

Lisa starred alongside Lesley Manville in BBC Two sitcom Mum, with comedies such as Hebburn and King Gary also on her CV. 

Yet Best Interests won't be her first prime-time drama and she has previously appeared in Inspector George Gently, Deadwater Fell, Maternal and No Offence

Des McAleer plays Eddie

Des McAleer Best Interests

Des McAleer plays Nicci's dad Eddie. (Image credit: BBC)

Eddie is Nicci’s dad, a former taxi driver, and Marnie’s sole surviving grandparent. Eddie is a gentle, compassionate Christian. He is the type of man who will turn up with homemade sandwiches during a crisis, who’s there to offer lifts to the hospital or a listening ear whenever they’re needed. He is gentle, soothing, and a great support for both his daughter and her family. 

What else has Des McAleer been in? 

Des recently played Barry Pettigrew in Hope Street and has also had roles in Silent Witness and The Crown. 

Mica Ricketts plays Hannah

Mica Ricketts Best Interests

Mica Ricketts plays Hannah.  (Image credit: BBC)

Hannah is Katie’s girlfriend, and Alice and Frank’s daughter. Hannah’s largely untroubled life has made her seek trouble where she can, often in life’s more illicit pleasures. She can be reckless and selfish at times, but there’s something in her that Katie is drawn to: her carefree nature, her supposedly adult life (the pretence of which serves to mask her immaturity and insecurity), the feeling that anything could happen when you’re with her. Their connection feels electrifying, and Katie feels seen by Hannah in a way that she isn’t by her parents. 

What else has Mica Ricketts been in? 

Mica starred alongside Katherine Parkinson and Jim Howick in sitcom Here We Go and has also starred in Bulletproof and As Dead As It Gets.

Mat Fraser plays Greg Richardson

Mat Fraser Best Interests

Mat Fraser as Greg Richardson. (Image credit: BBC)

Greg is a court-appointed guardian, the man tasked with figuring out what Marnie’s best interests are for her legal team, so they can represent her interests in court. As Greg can’t speak to Marnie directly, he finds her voice by speaking to those who know her best. Greg is an unorthodox, outspoken person, especially in the context of his profession, which usually relies on tact. But for Greg, his manner is not contradictory to his job: care means honesty.  

What else has Mat Fraser been in? 

A rock musician, writer and performance artist, Mat has been a drummer in several rock bands, including Fear of Sex. He has also played Richard III on stage. 

His screen appearances include roles in British dramas His Dark Materials and The Sister Boniface Mysteries

Shane Zaza plays Fred Hoozer

Shane Zaza Best Interests

Shane Zaza stars as Fred Hoozer. (Image credit: BBC)

Fred is Nicci’s solicitor, a seemingly friendly and accommodating presence in the often-daunting world of family law. Fred speaks as quickly and precisely as he thinks, but can break everything down plainly for Nicci, ensuring she knows about the legal process ahead and what they need to do to win. However, under Fred’s affable exterior he is a sharp, dogged lawyer, willing to use whatever information he can to build his case, gained by whatever means necessary. 

What else has Shane Zaza been in?

Shane has starred in British TV shows Doctor Who, Black Mirror, Waterloo Road and acclaimed BBC drama Happy Valley

Lucian Msamati plays Derek Frederick

Lucian Msamati Best Interets

Lucian Msamati plays Derek Frederick. (Image credit: BBC)

Derek is the QC for Nicci’s case, appointed by Fred. Derek’s an excellent, erudite barrister, but with an informal, conversational manner. In short, he’s someone you wouldn’t want to come up against in court. Derek’s approach is to be fearless and ruthless, aiming to test the limits of propriety in what is usually a civilised and sensitive area of law. If others will insist on playing nice, he won’t just play along to make life easy for them – not when these cases so rarely go the parents’ way.

What else has Lucian Msamati been in? 

Lucian is most famous for playing Salladhor Saan in Game of Thrones, but has also appeared in Gangs of London, Kiri and His Dark Materials

Sean Marland

Sean is a Senior Feature writer for TV Times, What's On TV and TV & Satellite Week, who also writes for He's been covering the world of TV for over 15 years and in that time he's been lucky enough to interview stars like Ian McKellen, Tom Hardy and Kate Winslet. His favourite shows are I'm Alan Partridge, The Wire, People Just Do Nothing and Succession and in his spare time he enjoys drinking tea, doing crosswords and watching football.