I feel as though I’ve grown up with Marian Keyes. Each of her novels represents a particular part of my life: she makes you laugh, cry – and feel that she’s on your side. Unbelievably, Keyes’ first book was published 25 years ago: “A quarter of a century! Thank you for letting me carry on doing this.”

Accompanied by her interviewer, the broadcaster and Booker Prize judge Alex Clark, Keyes had burst on to the Southbank stage like a ball of positive energy. She made us laugh by announcing “The amount of times I’ve come here with Himself to listen to classical music – and I know nothing about classical music. I only come because I know I’ll get an ice cream at the interval. Never in a million years did I think I’d be interviewed here!”

Keyes is in London to promote her new novel, ‘Grown Ups’, which introduces us to a new family: the Caseys. One of the characters is based on someone Marian has known for a long time and who recently acquired a new partner: “a terrible person”. Their collective group of friends recently went away for the weekend without this woman and “…we were all delighted and we had a harmonious break. But the next time I saw her I very nearly told her that we’d had such a lovely time because she wasn’t there!”

Looking aghast, Keyes continued “So, this book is about a person who can’t stop telling the truth. And a family that is very close and who, on the surface, get on well. Then Cora gets concussion and suddenly starts being truthful. That’s how the book starts and then we travel back in the six months before the accident – and a countdown to the day itself begins. The fall-out comes next.”

The Caseys are a blended family: a “good looking bunch, but messy on the inside.” Chuckling, Keyes confessed that she resembles Jessie, the eldest of the wives, who likes to stage-manage things: “I’m a self-confessed control freak.”

Family is a theme close to Marian Keyes’ heart and she was at her most entertaining tonight when talking about her mother, a devout Roman Catholic Irishwoman. Mammy K, it transpires, doesn’t hate ‘Grown Ups’ as much as Keyes’ other books, “…because there’s less riding than usual!” This redoubtable lady is the same age as Edna O’Brien, but would “happily have burned O’Brien’s books in the street” and was in full favour of their censorship. But: “She’s a product of her time”, mused Keyes.

And yet, Mammy K always believed in Marian’s talent. When Keyes returned to Dublin from London, fresh out of rehab, and submitted four chapters of ‘Watermelon’ to a publisher, it was Mammy K who went on pilgrimage to Knock, in County Mayo, and persuaded all her travelling companions to pray for Marian to achieve literary success. “It’s in the bag”, she told a disbelieving Marian at the end of a gruelling visit to the famed holy city – and sure enough, one week later Keyes was offered a book deal.

Mammy K, her daughter reflected, is “…a fantastic oral story teller with fantastic insight into people” – and Marian regrets that her mother didn’t have the same opportunities as her children. Instead, she had to give up her job when she got married, at a time when “Confidence in women was illegal in Ireland.”

As family informs Keyes’ novels so, inevitably, does addiction. Keyes has never made any secret of the fact that she’s a former alcoholic and regularly emphasises in interviews and on social media that her recovery is an ongoing process: “Being an addict isn’t something to be ashamed of – it’s a condition you’re born with.”

Reflecting on her gradual tumble into addiction, Keyes told us that, long before she took up drinking, she felt “like an oddball who hadn’t been given life’s rulebook.” Alcohol gave her the confidence she had always lacked – and after she gave it up, aged 30, she felt she had nothing to live for. “I tried to stay drinking as long as possible, and it felt like the end of the greatest love affair of my life. Our relationship had been passionate and thrilling, then it became grimmer and sadder and uglier. But still I mourned it.”

Keyes “realised the game was up” when she woke up one Monday morning with what felt like a pile of bricks on her chest. Having made a “lacklustre” suicide attempt, Keyes was carted off to rehab still believing that alcohol was the only good thing in her life. “At first, I looked around at the other residents and though “Poor bastards”. It took me a week to realise that I was one of them.”

Marian acknowledges that her books wouldn’t exist if she hadn’t undergone those experiences and believes that addiction has informed her writing in a positive way: “Writing about that feeling of alienation lets others know that they aren’t alone and it gives me a feeling of connection that I never used to have.”

As far as her fellow authors are concerned, the one subject guaranteed to get Keyes riled is that of “chick lit” (me too: I write about it here). “When men match humour with sorrow, they’re lauded for doing something wonderful. In fiction, as with anything, women are treated with less respect.”

Mind you: “I have strong views about EVERYTHING!” On the subject of asylum seekers, Keyes is particularly vociferous: “In Ireland, asylum seekers are not allowed to work and are made to sleep in dormitories, separated from their families. There are no kitchens, and nowhere to take friends. You can’t cook for yourself. All this is done so that Ireland is unattractive to asylum seekers”.

Keyes has been even more outspoken on the subject of abortion, publicly supporting – to Mammy K’s horror – the ‘Repeal the Eighth’ campaign. “I was genuinely terrified, but I’m proud that I did it and I’m even more proud of the thousands of people who put their livelihoods at risk to campaign.” The campaign’s success gave her, Keyes says, hope for the future, despite our unsettled political climate.

What’s next for this brilliant, hilarious, impassioned author? I have some exciting news to share: having always said that she would never write a sequel to any of her books – “My characters go through enough!” – Keyes has relented and is bringing back…drum roll please…Rachel Walsh. Yay! Although: “I’m wary. She’s older, I’m older, the world is different. And I don’t want to disappoint my audience. But I’m going to give it my best shot.”

I, for one, cannot wait.