Sitting at Kate and Gerry McCann’s kitchen table, watching their three-year-old twins Sean and Amelie playing on the floor, you could be observing any normal family scene. There are no histrionics. No weeping or wailing.

In the general melee of a family of four, it takes a few hours before the absence of their daughter hits you. But when it does, it is overwhelming. The crime that someone has committed against this family is colossal. Someone, somewhere, took Madeleine and in doing so they have come as close as anyone can to destroying the fabric of this family.

Until Madeleine is found, or someone comes forward to tell the McCanns what happened to their four-year-old daughter, they will be forever stuck just after 10pm on Thursday, May 3, 2007. It is a potential life sentence.

When I was initially asked to make a film about the McCanns, I didn’t immediately jump at the chance. I’d found it almost impossible to watch the news bulletins after Madeleine went missing and I didn’t want to make a film that merely indulged in witnessing at first hand her parents’ misery. And what could I say that hadn’t already been said?

I needn’t have worried. The McCanns, too, were uninterested in taking part in a “schlock doc”. They had a different agenda. For eight months they had been trying to ride the media train, with only one aim in mind – finding Madeleine – and every decision they had taken had had that goal at its heart. Now they had decided to add another one.

At our first meeting they talked about how much they had learnt about child abduction, how horrified they were and how they wanted to use their knowledge to try to make Europe a safer place for children. It seemed clear to me that they needed to find a more positive narrative for their lives. This new campaign, however long it might take, had the advantage of being both inextricably connected to finding Madeleine but different enough to provide some respite from the relentless pain.

Kate and Gerry were also well aware that the first anniversary of Madeleine’s disappearance on Saturday would rekindle media interest. And they decided it might be productive to try to channel that interest into a campaign that could benefit others.

There were numerous areas that they felt needed attention. Many European countries, they had discovered, do not require Criminal Records Bureau checks on people who want to work with children; many do not have a sex offenders’ register and many do not even have an organisation that deals with missing people, let alone missing children.

Two areas stood out. Soon after Madeleine had gone missing, they had been shocked to find there were no data collected on how many children are abducted each year. The figures simply don’t exist. And it’s not just mainland Europe that doesn’t bother collating them; no one can say for sure how many children are abducted in the UK. Part of the reason is that cases of abduction that end in murder or rape are logged only under the more serious category headings, which means the scale of the problem isn’t recognised.

The McCanns became convinced of the need for “child-rescue alert” – a system that is used with great success in America. There, as soon as a child is abducted, police issue radio and television station alerts. Even more impressively, they can also text-message mobile phone users in the area where the child was last seen with descriptions they may have of the victim and abductor, car registration numbers and other pertinent information.

The first few hours after an abduction are known as the “golden hours” because they are so crucial. Of those children who are ultimately killed after being snatched, 74% are murdered in the first three hours. And 91% are killed in the first 24 hours.

However, only four out of the 27 countries in Europe have a US-style system in place. There is no “child-rescue alert” in Portugal, where Madeleine was taken. In Britain, where we do have an alert system, it has been used only three times since it was introduced in 1997.

Once we started researching alert systems with the McCanns, it quickly became clear that they serve little purpose unless those police officers who are first at the scene of a child abduction are properly trained.

We followed the McCanns as they spoke to experts in London, Brussels and Washington about the mechanics of child-rescue alerts. After each meeting in America, the couple were visibly buoyed. First there was Ed Smart, father of Elizabeth Smart. Six years ago Elizabeth – then 14 – had been snatched from her bed. Her family had then worked tirelessly to keep her photograph in the papers and her story in the news. And for them it paid off: nine months later a passer-by spotted her with her abductor in the street.

She was reunited with her family – a living and breathing vindication of the tactic of keeping press attention high – for which the McCanns themselves have been criticised.

Some have even suggested that if Madeleine’s parents weren’t involved in her death, they probably killed her with the coverage – the implication being that their daughter’s abductor may have panicked at the attention the case was receiving and quickly disposed of her. So it was important to the McCanns to discover that Ed Smart had used the same strategy as they had; and in his case it had worked.

In Washington we also visited the National Center for Missing and Exploited Children – an impressive place, full of committed people who have the proper level of resources to combat child abduction. Since 1997, 393 children have been returned safely to their families because of a child-rescue alerts. And, in 33% of cases, the abductor actually gave up the child after seeing the alert himself.

There is no doubt in Kate’s and Gerry’s minds: these alerts save lives.

Crucially, the National Center has undertaken research that has given them fresh hope that Madeleine may still be alive. Even in the worst kind of kidnappings, just 40%-50% of children are murdered. The younger the child, the less likely that they will be seriously harmed.

The message from the statistics was loud and clear – until we know why Madeleine was taken and who took her, it cannot be assumed that she is dead. It was heartrending to see the McCanns’ hopes rising.

Over the course of four months we followed the couple as they researched child abduction issues and then launched their campaign at the European parliament in Brussels. There were many diversions along the way: more apparent sightings of Madeleine; venomous letters that dropped on the doormat and the leak of their first witness statements.

The McCanns have remained committed. Observing them has been a sobering experience. They live at the edge of human endurance, yet manage to survive. In fact they do more than survive. They are living. Their twins are almost obscenely happy, filling the house with love and laughter.

Kate and Gerry also remain strong. I was struck by how kind and generous they are and how they refuse to be defined by their tragedy. So as well as documenting their campaign for child-rescue alerts, I also wanted to show them as I found them – intelligent and brave but flawed, like everyone else I know. People who made a mistake – parents who made the wrong call.

Before Madeleine was taken, leaving your sleeping children while you ate dinner 50 yards away would have been a question of judgment. Some of us would have made the same decision as the McCanns, some of us wouldn’t. Thankfully, for the most part, our choices don’t lead to catastrophic events and so our parenting goes unscrutinised. For Kate and Gerry McCann, it did. And they are paying for that every second of every day.

I would not have thought it possible to survive the year that Kate and Gerry have just lived through. They have. I’m sure that friends who knew them before miss the people they were. But they resist being victims.

For now, they are determined to build something positive out of the hell of the past year. And they will never give up looking for Madeleine.

Madeleine, One Year On: Campaign for Change is being shown on ITV1 at 8pm on Wednesday

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