Telephone calls made by Jamal Zougam have been monitored, his many business dealings scrutinised and he has even been investigated for murder. Yet somehow this well-dressed 30-year-old Moroccan has been free to travel across Europe and North Africa and allegedly maintain contacts with some of al-Qaeda’s most wanted men.

Last night, all police would say officially about the suspect was that he had been “directly involved in the train bombings”. Nevertheless, he is alleged to have bought the telephones used to trigger the bombs left on four commuter trains last Thursday.

Terrorist investigators were first alerted to Mr Zougam a month before the September 11 attacks of 2001 on the United States. Agents searched the ground-floor flat in the Ciudad Lineal district of Madrid that he shares with his elderly mother, two sisters and a half-brother — another of the three men still being questioned last night about their alleged role in bomb attacks on four commuter trains.

Detectives have spent the past 72 hours questioning Mr Zougam on his alleged involvement in the bombings and alleged links with the Islamic group that killed 45 people in suicide bombings in Casablanca last May. He is also believed to have ties to terrorist suspects in half a dozen countries, including Britain.One leading terrorist expert in Madrid said last night: “The question the new Government will want to know pretty swiftly is: was there negligence? Could and should this atrocity have been stopped? Or is this the wrong man they have in custody and are the bombers still at large?”

Mr Zougam arrived in Madrid as a teenager. After being recruited by Muslim radicals, he passed through al-Qaeda training camps in Afghanistan and has been keeping closely in touch with some notorious terrorist figures.

To his friends, who know him by the nickname “El Angel” and say that the young man was a regular on the Madrid nightclub scene, there was disbelief.

Police tell a different story, however. His extremist leanings were obvious to those who searched his flat in Calle Sequillo on August 10, 2001. As well as violent books and videos, depicting killings in Afghanistan and Chechnya and tape recordings of Osama bin Laden, he had the mobile numbers in his diary of three leading names in an al-Qaeda cell. Some of those men still remain in custody at Madrid’s top-security prison.

It was the French authorities who had requested information on Mr Zougam after his name turned up in the address book of a wanted terrorist in Paris. Mr Zougam was questioned in Madrid, but he was released.

His telephone was tapped and his property was watched. His name should have been passed to border control to keep watch on his travels, but he went back and forth to Morocco many times and returned to Madrid just before the bombings in May in Casablanca of Spanish targets, including a cultural centre.

Detectives in Spain were already looking at his involvement in a mobile telephone business in Madrid’s main Muslim quarter, where he allegedly operated a credit-card fraud ring. From this shop, known locally as a locutorio, he helped immigrant workers to make calls to family at home and send money.

One of his customers was the man Spanish authorities name as the ringleader of the al-Qaeda cell in their country.

A few hundred yards from Mr Zougam’s apartment, he and his half-brother ran a thriving supermarket, which remained closed yesterday.

Neighbours such as Rosa García, 41, had not realised that the “well-spoken, very polite” shop owner was the man police have in custody. “People here will go crazy if they discover he has been plotting this atrocity in our neighbourhood,” she said.

'Warning' was on internet

The possibility of a terror attack timed to affect the Spanish election was being discussed by Islamic militants as long ago as December. A message posted on December 10 on the Internet newsgroup Global Islamic Media, which has previously carried statements purporting to be from al-Qaeda affiliates, suggested that attacks could help to bring about a Socialist victory and the withdrawal of Spanish troops from Iraq. It said it might also increase pressure on Tony Blair to withdraw British troops.

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