When Sara Payne's two sons were ten minutes late returning home from a friend's house one day, they found their mother crying her eyes out.

It might seem an over-reaction but this is a woman who knows how it feels to lose a child.

Eight-year-old Sarah was abducted from a field after straying from her brothers and sister on the way back from a beach near their grandparents' house in Kingston Gorse, near Littlehampton.

Her parents' desperate TV appeals ended when her body was found 16 days later, on July 17, 2000, in a field 15 miles away.

Four years on, Sara's grief is still palpable as she talks about life after Sarah. Her eyes are ringed with dark shadows, her skin is pale and she has the look of someone for whom sadness has become a way of life.

She has split with her husband Mike but says their new daughter Ellie has given them back a future.

When Sarah's parents discovered her killer was convicted paedophile Roy Whiting, who had previously abducted and assaulted another little girl, Sara began a controversial campaign, now known as Sarah's Law.

It aimed to change legislation to allow parents controlled access to information about individuals in their neighbourhood, including convicted child sex offenders.

The 35-year-old has written an account of those fateful days in A Mother's Story, which also charts the controversy surrounding Sarah's Law and the trial which ended with Whiting being jailed for life.

As a patron of the Victims of Crime Trust, Sara has met the families of other high-profile murder victims such as James Bulger and Damilola Taylor.

She said: "We all meet once a year. Although you'd imagine it would be a very sad meeting, it's not. It's somewhere you can go and be yourself. There's somebody there to listen."

July 1 is the worst day of the year for Sara, the day her daughter was abducted and the one guaranteed to envelop her in grief.

She says: "I never wanted to remember that date but we just can't get past it. I just know when it's approaching. You are aware of the sadness."

Life has seemed more positive since the birth of Ellie, now six months old.

"Last Christmas was better, being Ellie's first one. It gave us an excuse to put a bit more joy into it and decorate the house."

She split with Mike last summer but they have remained close and see each other virtually every day.

She says: "Ellie has given us back our future. We were existing day to day.

"Although people might think it's good to live for the moment, it's actually a very unhealthy way of living."

In fact, Sara was distraught when she found out she was pregnant and initially considered having an abortion, although it was something she said she could never have done.

She says: "Since Ellie has been born, Sarah has been in my thoughts. She was always in my thoughts but maybe in a darker way, more about missing her and her not being around. But now the living Sarah is part of my thoughts and I'm very thankful."

Is there more laughter at home now?

"We're getting there. Everyone's feeling a little bit more positive and less guilty about laughing and enjoying ourselves a bit more."

Since Sarah died there have been other family bereavements, including the death of Sara's mother and brother, while her father has been in hospital for two years with heart problems. Her other children, Lee, 17, Luke, 15 and nine-year-old Charlotte are getting on with life.

"Sarah's death shook their world. It made everything different."

Sara is much more protective of her children. Occasionally Charlotte is allowed to go to a friend's house but Sara just sits and frets rather than keeping herself busy.

When Sarah was first abducted, her parents came in for some criticism for leaving their children on a beach unsupervised. It's a decision Sara still feels guilty about.

She says: "You have to learn to live with it. I made a choice and I made the wrong choice."

She has also faced criticism from those who feel she is making money out of her daughter's death by writing the book.

She argues every penny will go into a trust for her children and she has turned down many other lucrative offers.

For a long time, the Payne household was an extremely unhappy place to be.

Mike was made redundant and the couple sank into deep depression and turned to drink, which sparked rows.

Sara says: "With each fight we were alienating one another more. We had to separate."

She hopes they will be reunited.

"We are working at things and we realise it's going to be a slow process. We need to deal with things on our own to be able to deal with things together."

Will July 1 ever become more bearable?

"No, because it's always going to be the day Sarah was taken," she says.

"I'd like to get to the point where one year I forget and look at the calendar on July 2 and realise the day has passed. Then I can say that time did heal."

A Mother's Story, by Sara Payne with Anna Gekoski, is published by Hodder & Stoughton, price £16.99.