Elaine Cassidy interview: 'Brian Friel is someone I felt I discovered for me'

London has been in the grip of the UK’s most relentless heatwave for 40 years. Spare a thought for the city’s poor actors, won’t you? When I meet Elaine Cassidy at the Donmar Warehouse, where she’s gearing up to star in Brian Friel’s Aristocrats, a rickety electric fan brings us small mercy. I have no idea how she’ll manage under the sweltering stage lights. But she’s chilled (mentally, if not physically). “I remember when we did The Crucible at the Gielgud, we had to wear hand-knitted woollen socks, for authenticity. And corsets. Beads of sweat would run down my leg!” she recalls, laughing.

Fittingly for the weather, the Irish actress, 38, is sunshine personified. Last seen on screen in Channel 4’s blackly comic detective drama No Offence, Cassidy is returning to a stage she knows well. The Donmar was the venue for her last theatre stint in 2015, when she stepped in at the 11th hour to replace Michelle Dockery in Les Liaisons Dangereuses ; in 2014, she starred in a production of Friel’s Fathers and Sons (also directed by Lyndsey Turner, who’s directing Aristocrats).

The timing was serendipitous for Cassidy. “Lyndsey, Friel, the Donmar, summer, a great part… yeah!” she grins. Aristocrats tells the story of a group of siblings returning to Ballybeg Hall, the old country pile they grew up in that is now a far cry from its former glory. Cassidy plays Alice, and she talks about her like a dear friend. “I really like her. She’s really sad. I think she knows her life is pathetic,” she tells me. “I think she’s more aware, like: ‘Things are s*** now. Things used to be great, we went to finishing school and we became young ladies… and now I’m an alcoholic’.”

London is having a bit of a Friel moment, with his 1980 play Translations currently running at the National Theatre. So, why stage Friel now? “I mean, I think every day is a good day to do Friel,” Cassidy says. The Irish playwright, who died in 2015 and is considered one of the greatest writers of his time, holds a special kind of magic for Cassidy, who met him twice: once at the age of 19 after an audition (she didn’t get the part — she was too young), and again after the opening night of Fathers and Sons.

“He was someone I felt I discovered for me,” she says. “I can tell my grandchildren, at the age of 19 I got to meet the man — and isn’t that incredible?” She recalls how he shook everyone’s hand one by one after watching their production of Fathers and Sons, “and I felt so overwhelmed I nearly cried in his face, it just meant so much.”

Cassidy has previously spoken about having a breakdown on stage at the end of a particularly draining run. How will she cope with eight weeks of playing a character troubled by such darkness?

She laughs the laugh of someone who’s had enough time to see the funny side. “I’m always really naïve when I start a job. Every time, I say to my husband [actor Stephen Lord], ‘I don’t think it’s going to be too taxing, this one’. Cut to: hhnnngghhh! Snot coming out everywhere!” she says, gesturing wildly. Theatre always takes a lot out of her, she admits — it’s a matter of preserving your energy.

You could say it’s fitting that we’ll be able to watch Aristocrats, about a once-powerful generation now in decline, in the wake of the successful campaign in Ireland to repeal the 8th Amendment. The pace of change in the country in the past 10 years has been immense; the previously ultra-conservative republic now has an openly gay prime minister and voted to legalise gay marriage and abortion rights. How does it feel for Cassidy, who is from Raheny, to watch that happen from afar?

Her already effervescent tones reach full animation. “I was raging I couldn’t vote!” (As an Irish citizen but a UK resident, she was unable to have a say.) “It’s incredible, and it’s brilliant — but on the other hand you think, ‘Oh my God, only now?’”

Although she speaks with fondness of Ireland, where strangers talk to each other on the bus, Cassidy has no plans to move back. She doesn’t miss the draining commute to the UK that defined the first five years of her career, and she loves the fact that London is the city she chose.

“Someone said, you can spend a lifetime in London and still never know it. I love that: sky’s the limit, no ceiling,” she says. It’s an ethos she wants to pass on to her nine-year old daughter and five-year-old son.

Cassidy hits the big screen with female comedy ensemble Strangeways, Here We Come in October, and No Offence has just filmed its third series. Representation for women is steadily improving, so we might finally be able to say that the sky’s the limit for actresses too. Does she really think we’re getting closer to achieving a better balance? She gives it some thought, before sounding almost apologetic about her idealism.

“Stupidly and naively, I’ve just grown up knowing that everything should be equal, so I take that view. Our attitudes to everything have to change: relationships, gender, beauty.” And then her face lights up again. “It’s all up for grabs.”

Aristocrats is at the Donmar Warehouse, WC2 from Thursday to Sept 22; donmarwarehouse.com