Edgardo Alvarez would probably never have been caught were it not for the events of September 11, 2001.

The 65-year-old vanished with his daughter Esmeralda, then six, in July 1999 and sparked an international police hunt which lasted four-and-half years.

Detective Sergeant Stuart McColl of Crawley police, who led the operation to find Alvarez, said the search started fruitfully with many reported sightings throughout Europe but tailed off as the months wore on.

Alvarez's whereabouts remained a mystery until December last year.

Only since his arrest have officers been able to piece together the former Spanish lecturer's movements across the globe.

It appears Alvarez left England almost immediately after abducting Esmeralda. Travelling on his British passport, he went to France, then moved quickly to Italy.

He then entered Turkey, where he spent a week buying false identification papers to secure his path through US customs.

Once in America he settled in Miami for six months but was arrested for fraud and moved before the authorities could discover his true identity.

Mr McColl believes Alvarez could well have hidden for good among America's millions of Mexican immigrants but after the atrocities of September 11 the country changed overnight.

He said: "Before then it was relatively easy to travel through the world, especially as father and daughter. But after the terror attacks on the Twin Towers, American security was stepped up and it was only a matter of time."

The lucky break came when Alvarez was arrested for speeding near his new home in the small Utah city of Ogden, about 40 miles north of Salt Lake City.

The traffic police held him in custody while detective Dale Bridges, a member of the country's Homeland Security department, checked his background.

Mr McColl said Alvarez was exhausted and practically penniless after four years on the run and confessed all when challenged about his true identity.

He said: "I think he was very down on his luck at the time and it was a really low moment in his life. I don't think he would have ever given himself up but as soon as he had to use his brain to stay ahead of the police he just didn't have the energy."

Things got so bad for Alvarez he had actually given up looking after young Esmeralda. She was being looked after by a devout Mormon, Connie Grosshans, who took pity on the youngster after seeing her alone on a cold night without a coat.

Mr McColl, who travelled to Utah in December to extradite Alvarez, is immensely relieved Esmeralda's ordeal has ended free from tragedy.

He said: "Our biggest fear was for the young girl's safety as you never know what can happen in four years.

"What Alvarez did was awful - to leave everyone in the dark and not even let her mother know she was alive is just despicable.

"But bringing an end to this case is wonderful for the family and I'm just glad there has been a happy ending."