If Cecelia Ahern’s career had gone according to her initial tentative plans, she guesses she would “probably be making tea or coffee for a director somewhere” about now, trying to get a foot on the film-making ladder.

Instead she is the best selling author of six novels, the first five of which have already been optioned to be made into movies, starting with her debut book PS I Love You, a romantic weepy that hit the screens earlier this years starring Hilary Swank and Gerard Butler.

Not only that but she was invited by the head of comedy at the American television network ABC, after she read and fell in love with PS, to come up with an idea for a sitcom. The result was the Emmy award-winning hit Samantha Who?

As if that wasn’t enough, she even beat Jane Austen in a poll to find the best chick lit of all time.

It is mentioning this last statistic that leaves the 27-year-old daughter of former Irish Taoiseach Bertie Ahern, at a momentary loss for words.

“That is quite incredible,” she admits. “I don’t know what to do with that piece of information. I think there was a survey done on great love stories and PS I Love You came among the list.

“It is an absolute honour,” she finally concludes.

Cecelia is articulate yet reserved when talking to the press, her adeptness at fielding questions is something she has been learning since the age of five due to her father’s high public and political profile.

“I think we were always aware and very careful about who we spoke to and about what we did,” says Cecelia, who has an older sister Georgina, who is married to Nicky Byrne of Westlife.

“We were talking to journalists all the time, answering the phone from the age of five, and just knowing what to say, though we were never sat down and given a masterclass.

“I think we learned a lot from it. I understand how things work. I don’t read the newspapers and I don’t take anything personally.”

She studied to be a journalist, completing a degree in media communications at Griffith College Dublin.

Prior to that there had been an abortive attempt at a singing career as part of a group called Shimma, who came third on the Irish version of a Song for Europe. Though she had studied dance as a child she decided she was more interested in showbusiness from the other side of the camera and embarked on a masters in film production.

“I went in for two or three days and eventually left to write PS I love You. Right now I would probably be making tea or coffee for a director somewhere. That was the route I was going to take.

“I have jumped the queue a bit”.

She wrote the novel when she was 21 – not for publication but for her own amusement. She only sent it to a publisher at her mother’s urging.

“I started writing it for myself. That is what I have been doing all my life, as soon as I get an idea I write it down,” she says.

“From the age of eight I have been writing stories and poems and never thought of it as a career.”

The book, about a young widow whose husband arranges to have a number of letters delivered to her after his death to help her come to terms with losing him, was the No 1 best seller in Ireland for 19 weeks and was also a hit in the UK and the US.

When it was made into a film, Cecelia was prepared to see her story completely transformed, but apart from a change of location to America and a change of nationality for her heroine, it remained much the same.

“I was excited to see someone else’s interpretation of it,” she says. “I separated myself from it, like the book was my baby and the film was Richard LaGravenese’s (the screen writer and director).

“When I saw it I just felt like he captured the whole heart of the story, what people had loved about it which was it made them laugh and it made them cry.

“I just think it is fantastic. I have seen it about nine times now and every time it gets me I am very proud of it.

‘The quality of the cast is amazing. A two-time Oscar winner – you can’t get any better than that. And it was nice to see Hilary doing something comedic.”

It was while she was busy promoting the film as well as publicising her fifth book that she got the idea for her sixth, The Gift.

It is a modern fairy story about Lou, an ambitious executive who is neglecting his family to further his career until he miraculously finds himself able to be in two places at once.

“I just absorb things from life. I’ll be day dreaming and next thing an idea will pop into my head,” says Cecelia.

“I was being pulled in all sort of different directions and I needed to be in two places at the one time. I thought if you could do that where would you chose to be, what would you learn from it?”

The inspiration for her fifth novel, Thanks for the Memories, about a woman who starts remembering things experienced by her blood donor, came after she saw an ad showing someone receiving an injection and started pondering how people can be intimately connected without even realising it.

Then she saw a documentary about people who had received heart transplants and begun exhibiting the personality traits of the organ’s former owners.

When she visits Birmingham tomorrow for a book signing at Selfridges, Cecelia will first drop into the blood donor centre in New Street where she will be handing out free copies of Thanks for the Memories to anyone depositing a pint.

Though her stories often contain elements of the fantastical – in one of her novels an imaginary friend becomes flesh and in another a place actually exists where all the lost things collect – she says her characters are just everyday people in extraordinary situations.

She seems remarkably untroubled by the anxieties that might afflict other authors.

She admits there are days when she has been banging her head against the table trying to move the plot along but she has never really suffered from writer’s block, or the fear that her second novel wouldn’t be able to measure up to the success of the first. And she has never faced a deadline she couldn’t meet.

“I have OCD when it comes to deadlines, I have always been handing things in early.”

Her boyfriend of eight years, athlete turned actor David Keoghan, is, she stresses, very understanding about her nocturnal lifestyle.

“He is acting so he is not a nine to fiver either and he can travel with me when he is not working. You can make anything work when you want to.”

She will be signing copies of The Gift at Selfridges tomorrow from 6.30pm.