Dear Kate,

Can it really be only three years since your little daughter Madeleine disappeared?
 It feels like a century ago when her three-year-old face first began to haunt us.

Her angelic expression and solemn eyes engraved themselves on to our hearts; they reached out to us from posters that went up everywhere, from airports to village shops.

Even now, the questions remain. Could she still be alive? Worst of all, is she the prisoner of some twisted individual? I know that must be your deepest fear - indeed it doesn't bear thinking about - although of course it must always be at the back of your mind. 

Over the years we have shared your nightmares. In those early months, as news story followed news story, we pored over the events of that fatal evening she went missing. You must have relived those hours a million times, and so have we.

So I hope it doesn't sound too harsh to suggest that three years later, the world has moved on. Not because we have forgotten Maddie, nor because we have lost sympathy with you and your family, but because the pain we felt at the time has begun to numb and heal with time.

No doubt that's what motivated you to appear on GMTV yesterday. To remind us. To shake us into caring again. Clearly you are still in agony - perhaps, for you, time has even intensified it. As you and Gerry publicly accuse the police of 'giving up', it is obvious that your agony is caused not just by loss, but by not knowing if your darling girl is dead or alive, safe or suffering.

Advice: Esther Rantzen believes the McCanns need a positive memorial to celebrate Maddie's life

You are still tormented by the fact that nobody can answer your questions, because Maddie has not been found, and may never be found.

Let us for a moment face the tragic truth. Maddie may not be alive. How will you feel if one day her body is found? My guess - and it can only be a guess because no one can truly know how you feel - is that after the first terrible impact of shock and grief, you may even feel a small glimmer of relief that at least she is at peace.

That is not in any way to diminish your terrible loss. It is simply a human response to your current purgatory. No more guessing; no more false hopes cruelly disappointed. Perhaps the fact of knowing might bring with it the understanding that, at last, you might be able to move on with your lives.

For at the moment you are still stuck exactly where you have been for the past three years. As you say yourself: 'As a parent of an abducted child, I can tell you that it is the most painful and agonising experience you could ever imagine. My thoughts of the fear, confusion and loss of love and security that my precious daughter has had to endure are unbearable.'

So maybe if you knew the truth, no matter how tragic that truth is, you might find it easier to bear.

You are not alone. Parents who lose children have told me how important it is to have something, even a body, to centre their grief on. I remember interviewing Winnie Johnson, mother of Keith Bennett. Keith was one of Ian Brady's child victims, murdered and buried somewhere on the Lancashire moors, the only child victim whose body was never found.

Unlike you, Kate, Winnie has known for years that her child is dead. But like you, she is still tormented by not knowing where he is.

Keith's murder took place 46 years ago. Yet only a couple of months ago Winnie took a helicopter flight over Saddleworth Moor to search for her boy's body yet again. And to pray for him.

She said: 'I know these moors go on for ever, but I know one day we will find my Keith. I will never give up hope. I want him back. I will fight for ever more until I find him and I hope I will find him before I'm dead.'

Although Manchester police have called off their search for Keith's body, Winnie is appealing for £20,000 to pay for a special scanner powerful enough to find buried remains. After nearly half a century of uncertainty, she still yearns to find him, to be released from rage and pain, and be enabled to grieve.

Make no mistake, that need to mourn a lost child is one of the most powerful emotions a mother can feel.

Agony: For Gerry and Kate McCann, pictured during their interview on GMTV, the torture continues

I once made a television programme about still-born babies. At the time, it was the practice to try to pretend the babies had never existed. Fathers were told to go home and redecorate the nursery and give away the baby clothes. Hospitals buried the tiny bodies in unmarked graves.

There were no photographs taken, nothing to remind the parents of their loss. Annihilating every trace of the child was considered the kindest way to help a grieving mother cope. But it was terribly wrong. Bereaved parents told me that years later their grief was as fresh as ever; that they had constant dreams and flashbacks of the baby they had lost.

So now the practice has changed completely. Doctors and midwives encourage parents to create memorials, books and gardens for still-born babies.

Grief, mourning and a carefully created memorial can bring healing. Which brings me to another family in despair.

Seventeen years ago, when he was a toddler, James Bulger was brutally murdered by two children, Robert Thompson and Jon Venables. That murder is engraved on our national memory and broke his mother Denise's heart.

For 15 of those years she has been unable to leave her home alone. I have visited her there, in the house that had become a shrine to James. All she had were constant reminders of his terrible death, not of his life. 'He was such a positive little boy,' she told me, 'I'd love him to have something positive to celebrate him with.'

So I suggested to her that we could create a special memorial to James, a project on Merseyside, her home town, to help children who have been badly bullied. Run by the Red Balloon charity, it could be called James Bulger House.

When Denise visited a Red Balloon project with me and saw their fantastic work in giving traumatised children their lives back, she leapt at the idea of a similar project in her son's name. 'I would love my children to have a positive memory of James,' she told me.

James Bulger House is about to open now; there are already children on its waiting list. And on what would have been James's 18th birthday, Denise took 18 red balloons to his graveside.

Why is this relevant to your own terrible heartache, Kate? Well, what I am suggesting is that you and Gerry need a similarly positive memorial to celebrate Maddie's life, too. Not because I am assuming she is dead, but because when we last met I saw how frail you are, and how unhappy. And no wonder.

I know that you and Gerry are constantly with parents of missing children who, like yourselves, are lost in the no man's land between grief and hope.

The work has inevitably immersed you in the hideous world of child pornography and sexual exploitation, because that is often the motive of those who abduct children. You say that now you know about 'the unbelievable existence of such a horrifying activity and its vastness in our socalled civilised and "child-loving" society', your eyes have been opened to a terrifying new world.

With that nightmare constantly before your eyes, no wonder you accuse the police of 'giving up' on Maddie. Let no one judge you harshly for keeping the flicker of hope alive in your hearts.

But alongside your campaign to tighten laws against child pornography, why not also create a Madeleine McCann charity - one that would not simply fund the search for your lost daughter, and others like her, but which would also help children in other distressing situations?

It could be medically based - perhaps as Gerry is a consultant cardiologist, it might work for children with heart disease. Or perhaps it could provide respite for families battling with disability - for example, the thousands of children who spend their exhausted lives helping to care for a disabled parent, day in day out.

These are only suggestions. You as a GP and Gerry as a consultant must already know many other ways in which you could give practical support to other children, in Maddie's name. And the happiness you create would surely give you both the strength to heal the past, and optimism to face the future.

In the meantime, be assured, we have not forgotten Maddie, or you. But we recognise, in your anger, that time has stood still for you.

And although we would not wish you to lose your commitment, we would also like to feel that you find comfort in the knowledge that Maddie's name will live on, and will contribute happiness to many other children's lives - wherever she is.

Wishing you happiness as ever,

Esther