Novelist Cecelia Ahern has announced that she has completed a sequel to her debut novel, PS I Love You, and has said that she hopes readers will "ugly cry" through the story as much as she did when she was writing it.

The follow-up to the hit book, which was adapted into a movie, is titled Postscript and will be published in autumn and catches up on the story of husband and wife, Holly Kennedy and Gerry Clarke.

PS I Love You, published in 2004, was about the couple’s relationship and how Holly received ten envelopes after Gerry's death - one for each month after his passing - containing messages from Gerry to his wife, all ending with "PS I Love You".

The first book became a Number One best-seller in Ireland and stayed on the book charts for 19 weeks.

Ahern announced the news of the new book on Twitter on Monday, writing, "I’ve done it. I’ve written the sequel to PS I Love You and it’s titled Postscript.

"It’s the PS to my PS of 15 years ago and writing it has been an emotional experience. I don’t know how I’ve succeeded in keeping this a secret for so long but I’ve been bursting to share it.

Hilary Swank and Gerard Butler starred in a film adaptation of PS I Love You

"Postscript will be published this autumn. I hope you’ll welcome back Holly...and Gerry...and ugly cry through the story as much as I did."

Hilary Swank and Gerard Butler starred in a film adaptation of PS I Love You, which was released in 2007.

Ahern, the daughter of former Taoiseach Bertie Ahern, went on to become an award-winning author who has been published in nearly fifty countries, and has sold over 25 million copies of her novels globally.