I should have done more
'Sarah, like a lot of teenagers, caused some heartache during adolescence. One turning point came when she was 11 years old and my son Andrew died. He was 27. Sarah loved her uncle - we all did - but they were soulmates. He encouraged her in everything - her music, writing poetry. They went for long walks in the woods together and he taught her the names of birds, trees. But sadly, he suffered from depression and died of an accidental overdose.

It all happened so quickly. I should have done more for her then, but my own adored son had died. Sarah cried all the time and later got very bitter and angry. We should have got her counselling, but we were so caught up in our own grief.

After that, she started to change. Maybe it was a cry for help. She ran away on a regular basis - always overnight, was dabbling with drugs and got in with a wild bunch. We found each other hard to understand, but we never broke the bond. She'd still fling her arms around me and say: 'Hello Nanny, I love you'.

Sometimes we'd talk or she'd sit on the floor at my knee and we'd watch telly together. It's hard for anybody to admit their children are on drugs, but she was. She started to run away two or three days at a time and I did get very angry with her.

She'd say, 'Oh Nan, you're so old fashioned,' and I'd try and say, 'But these things are important, how you sit, how you dress, how you eat, how you talk to people.' Even when we weren't getting on, after I'd said my piece, she'd hug me.

The only time I really ever lost my temper was when I found out that she'd been inhaling some of my body spray up in the bathroom. I found out later that you can get high on that and I flew at her: 'How stupid can you be, you could have killed yourself.' But mostly I was her Nan, always happy and jolly and a bit old-fashioned, but not a dragon.

Her mother couldn't cope
Her running away got worse however. When she was 14, it was once or twice a week. By then my daughter Victoria, who remarried when Sarah was six, had two other children, Anya and Josh, and it was hell for her. She used to walk the streets late at night checking car parks till two or three in the morning. Eventually, she couldn't cope.

She contacted social services and they put Sarah in a children's home in Northampton. It was a voluntary placement; they thought a different environment away from her gang might help. There were no locked doors or barred windows. She could come and see me or her family whenever she wanted.

But here is a big regret. Before she went into the home, she said to me: 'Nan, can I live with you?' And this is something I'll suffer about to my dying day - I said no. I had a lot of health problems, suffered from shortness of breath and had to give up work as a call centre advisor four years ago. The illness was frightening and stressful and I couldn't cope.

When she went missing for the last time, the police were backward in coming forward. They just said, 'Oh that Benford child has gone again.' At first, we all thought she'd come back like before but she didn't. After a while, Victoria wrote a 17-page letter begging the police to do something, but by then all the leads had gone cold.

After that, detectives came three times to Victoria's house and searched it from top to bottom, thinking Victoria might have murdered Sarah. That really hurt.

We're always looking
The first week she was gone was awful but the longer it goes on, the worse it gets. My thoughts move round and round all day. As a family, we've done everything we possibly could. Victoria contacted everyone Sarah knew - relatives, acquaintances; we've searched local towns. My son Stephen, who works all over the country, has put posters up everywhere: hospitals, train stations.

On some level, every time you go out, you're looking for her. We try not to let this take away from the childhood of our other children, but it's so hard. Her brothers and sisters are desperate for her to come home and even now, on my birthday, they sent me a card saying 'To Nan, love from Sarah, Anya and Josh'.

Before Christmas, our hopes were high - there was a new detective on the case, the police had got more active, there was a press conference. But since then, there's been nothing. Over New Year, Victoria was so depressed that she couldn't handle it anymore and ran away herself for a while.

My worst fear now, which I can't voice to my children, is that Sarah might have been abducted, kept on drugs, perhaps used as a prostitute.

We're ex-directory, but every time the phone rings I jump. My first thought is 'Is it Sarah?' Every night when I go to bed, I talk to her. I say, 'Sarah, you didn't come home today, but you might come home tomorrow, or next week.' I tell her I love her to bits. Then I try and go to sleep.'