"As a mum, I was meant to protect my children and to know what to do if things went wrong. I had failed on both counts."

The murder of eight-year-old Sarah Payne horrified the nation. Now her mother, Sara, has written a book recalling the hideous events. Eric Roberts reports.

The nightmare which Sara Payne and her husband Mike went through is unimaginable.

For 17 days, their daughter Sarah aged eight was missing, her school photograph on the front page of every newspaper in the country. When the little girl was found, victim of a brutal murder by paedophile Roy Whiting, her mother's reaction was "Thank God", indicating the relief that she at least knew what had happened. And in her new book, Sara says she had a strange premonition that she would never see her daughter as a grown-up.

Whiting's trial and conviction, after which it emerged that he had been previously convicted for abducting and sexually assaulting another little girl, were a traumatic period for the Paynes, during which they started a high-profile campaign for the passing of a law to name and shame sex offenders. In private, they were battling against alcoholism and fighting each other.

The arrival of baby Ellie, now almost six months old, has helped them to move on, and Sarah says she's grateful to Ellie, although she confesses she will always be over-protective towards her.

Of her memories of the trial, coming face to face with Sarah's killer, she says: "I'd expected some sort of monster, but he was just a nothing – a greasy little man who would have been terrifying to a young child but who posed no threat at all to an adult. He wouldn't look me in the eye."

Despite what happened, Sara isn't in favour of the death penalty. "I don't think we have the right to take anybody's life," she says, simply.

Although Mike left her as their problems mounted, she hopes they may get back together. "We're getting on better, and he's my soulmate," she says. "He comes round every day; whereas before he was spending most of his time in the pub, now he has a new lease of life, his depression has lifted and he has started looking for work again."

Written with journalist Anna Gekoski, her book recalls her decision to allow Sarah to play on the nearby beach with three other children: "There were four of them, it was still light, and the beach was almost deserted. We couldn't see what harm they could possibly come to."

It emerged that the children had wandered to play hide and seek in a field nearby, and that Sarah's brother had lost sight of her. After searching frantically for her themselves, the family called the police. Sara recalls going to the field as dawn broke the next day, falling on her knees and sobbing and screaming: "As a mum, I was meant to protect my children and to know what to do if things went wrong. I had failed on both counts, and I wasn't sure that I could stand it. If Sarah wasn't there, I didn't want to be there either."

Sara subsequently presented to the public an image of almost unnatural calm, but when Sarah's body was found 17 days later, she and Mike sobbed together: "Through my sobs, I managed to say, 'I want to see my little princess',"

Amid the many letters of condolence was one containing a tirade of abuse against the family, accusing Mike of having killed his daughter. He had to be interviewed at length to eliminate him from the inquiry, but within a week of Sarah's disappearance, Roy Whiting was being named as a suspect.

Sara says that Ellie's birth has reminded her that there is something to live for: "She has given me back tomorrow. But the pain never stops and never will. There is no point in fighting against it, you just have to learn to accept it and incorporate it into your life.

"I will always have five children and one of them will always be an eight-year-old girl, but I can't spend my every waking hour mourning for Sarah. I still love and miss her like crazy, but I have finally accepted that she is never coming back. With this acceptance, the darkness that has engulfed me for so long has finally given way to some light."

Sara Payne: A Mother's Story is published by Hodder and Stoughton at 16.99. To order a copy through the Yorkshire Post Bookshop, phone free on 0800 153 32 32. P&P is 1.50.