'I’ll never write a sequel,’ Cecelia Ahern told her publishers when her 2004 novel, PS, I Love You, became an international bestseller, shifting more than 25 million copies worldwide. And when the box-office hit film adaptation starring Hilary Swank and Gerard Butler came out three years later, the author stuck to her guns.

‘I’d brought Holly [the book’s protagonist] to where she needed to be,’ she says of the widowed heroine who starts to receive a series of letters from her husband, designed to ease her grief, on her 30th birthday. ‘There was no story. And I couldn’t help thinking: “The first book made my career. What if this one breaks it?”’

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But seven years ago, something curious happened. ‘I had to change my will after the birth of my second child,’ says the 37-year-old, soft-spoken Dubliner with sparkling eyes, who is pregnant once again. ‘So I was thinking about guardianship and the everyday things that we do to prepare the people we love for when we’re gone – and that just opened it all up for me. PS, I Love You is written from the perspective of the person left behind; I wanted to write the story of those preparing to leave. This could be it, I thought; this could be the sequel.’

Postscript is unlikely to disappoint Ahern’s fans. Set six years after Holly Kennedy read her husband Gerry’s final letter, the book begins with a snapshot of the life Ahern’s evolved heroine has finally been able to live.

‘As I reread PS, I Love You for the first time in 15 years, I’d started wondering whether Gerry had done the best thing for her, leaving all those letters,’ says Ahern.

Most of us would feel pretty smug about writing a bestseller at 21. But Ahern says coming back to the book years later was an uncomfortable experience. ‘I did it through parted fingers,’ she winces. ‘Because it was a bit like reading an old diary.’ Nevertheless, there were moments where she was pleasantly surprised by the purity of the writing. ‘And a couple of times, I thought: “Wow, that’s pretty deep for a 21-year-old.”’

So deep were both the premise and tone of PS, I Love You that alongside the praise came a few snide comments. As the daughter of the former taoiseach of Ireland, Bertie Ahern, and a girl who had never lost anyone close to her, what did Ahern know about death and mourning? Had she – whisper it – even written the book herself?

‘People thought they knew about me and my life – when actually they had no idea,’ she says.

However gilded her life looked from the outside, she admits now that her hit novel came from ‘a very dark place’. Describing the inner torment the once-bubbly dancer and Eurovision hopeful was too ashamed to tell anyone about at the time, Ahern says: ‘I hadn’t lost somebody I loved, but I had suffered a huge loss of identity that had made my world very small and sad. I wasn’t sure who I was and where I was going.’

PS, I Love You has sold millions of copies worldwide
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Only after experiencing crippling panic attacks did she realise that there was a name for the anxiety disorder she had been suffering from for years. She recalls: ‘I’d always hated public speaking. Whenever it came to reading aloud in class I would have a plan, like excusing myself and going to the toilet. But over time I had started avoiding more and more scenarios, and, at 19, my first panic attack came out of nowhere.’

Ahern was on a bus on her way to her first day at Griffith College, Dublin, where she was to study film production, when it happened. ‘People think anxiety is about “being a worrier”, but it’s not,’ she says quietly. ‘It’s a physical sensation. I couldn’t breathe; I was too hot. Things are distorted and you get this fight-or-flight feeling, this desperate need to just get out – go.’

Thanks to the opening up of the mental health conversation, people now are far less likely to dismiss anxiety as an overreaction or even an indulgence. And for that Ahern – who dropped out of college that same day and struggled for years to find a way to manage the disorder – is grateful. ‘The conversation has completely changed,’ she nods. ‘I couldn’t talk about this for ages – and in some ways I hate that I even do now. And yet it’s important.’

Ahern tried cognitive behavioural therapy and hypnotherapy, but really it was the writing that provided the biggest deliverance – allowing her to escape into a new fictional world with each of her 13 bestselling novels, and vent a whole smorgasbord of female frustrations with the 30 allegorical short stories compiled into her critically acclaimed 2018 book, Roar.

Having children also helped quash the anxiety: she and her producer husband of nine years, David Keoghan, have seven-year-old Sonny and nine-year-old Robin. ‘You are their voice and you have to speak up for them,’ she says.

Does the disorder ever really go away? Ahern thinks about this. ‘I don’t have to abandon shopping trolleys in supermarkets or suddenly leave a queue in a post office. Now it’s only if I’m about to go live on some big TV show or to an important meeting. But I’ve learnt how important it is to look after yourself beforehand: eating well, exercising and practising breathing techniques.’

Ahern will have plenty of need for those over the next few months as she travels from her home in Malahide to Hollywood to work with Nicole Kidman on the TV adaptation of Roar.

Due out next year, the series of short films will be executively produced by Kidman and Per Saari’s Blossom Films, and feature a different actress in each story, from The Woman Who Found Bite Marks on Her Skin – an account of maternal guilt – to The Woman Who Slowly Disappeared – about an older woman who becomes invisible.

Written before MeToo and published just after Weinstein’s exposure, Roar was described as “feminist short stories” by The Bookseller, Ahern tells me. ‘Which made me laugh, because my books have always had a strong female voice: never have I had heroines being carried off into the sunset.’

In a wonderful irony, the idea was sparked by a Hollywood meeting with a casting agent years ago. ‘“We want characters in their 30s”, he was saying, “because we’re led by advertising and they’re the greatest consumers.” And I thought about my mum who did loads of shopping and watched loads of TV in her 50s but never saw herself reflected in any way, and thought: this is why women feel invisible as they get older.’

Refusing to become a part of ‘a machine I found horrible’, Ahern flew back and ‘immediately wrote a screenplay called Old about characters in their 70s and 80s’.

From the girl who had to get off that bus to the one sitting in front of me now is quite an evolution – one she became acutely aware of in that rereading of PS, I Love You. ‘Because in the opening chapter Holly talks about how, after so much time wanting to hide, she now needs the light. And it made me wonder how much I’ve transformed...’

Ahern gives a tiny shrug, embarrassed, perhaps, that she might sound too earnest: ‘Well, maybe now I need the light, too.’

The Daily Telegraph