Operation Cathedral, which led to the smashing of the world's largest internet child porn ring, began in San Jose, California, in 1996.

A child complained that her friend's father molested her and when police investigated they found the abuser had published the act on the internet.

The material was distributed to members of a paedophile ring called the Orchid Club and police discovered that among its subscribers was a man living in St Leonards, Hastings.

Officers contacted Sussex Police, who later identified the man as computer consultant Ian Baldock, 31, of Upper Maze Hill.

Officers raided his home and seized his computer. They found pornography linked to the Orchid Club and a yet more sinister paedophile network called Wonderland.

By checking web site addresses and service providers, police were able to identify members of the club throughout the world.

Two Sussex officers, who cannot be named because of their covert activities, joined colleagues from the National Crime Squad to prosecute the offenders.

They discovered Wonderland members could only join if they provided 10,000 images of children different from those already on Wonderland's database.

Detectives were sickened by the images they found. Ten officers at Crawley police station viewed hundreds of thousands of pictures of child sex abuse.

They saw more than 400 boys and girls aged from infancy to puberty. One was a baby less than a year old.

Several months of investigation helped police identify 100 subscribers in 12 countries and the plan for simultaneous raids was set in motion.

They were carried out on September 2 1998, and each suspect's rooms were photographed to see if they could be identified in any child abuse pictures.

In the background of some of the internet pictures police picked bedclothes, toys and furniture and even now senior officers hope they can trace victims and rescue them.

The officer in charge of Operation Cathedral, Detective Superintendent John Stewardson, has even considered publishing "cleaner" segments of the pictures and photographs of the children's faces in the hope people will come forward with information about the victims.

Police in Sweden are setting up a database to catalogue images of child pornography.

Police forces around the world are determined to crack down on child abusers using the internet but some senior officers doubt whether it can ever be properly policed.

One told The Argus: "With millions of world-wide transmissions going on, how can any force keep tabs on what is being sent round?"