He told his family he was going to London with friends for a few days, but on Thursday evening [earlier reports 10am on July 7 - Ed], when he failed to return home, his mother called the police to report that he was missing. The phone call would help police break open the case.

Mr. Hussain's driver's license and bank cash cards were found in the wreckage of the double-decker bus.

The man had been on Britain's terrorism watch list but was still allowed to enter the country. One of the officials said the suspect is one of several foreign citizens whom investigators are seeking but cautioned against speculation that he had engineered the attacks.

Blair confirmed that the suspect was not placed under surveillance when he came to Britain last month because he was not classified as a high risk. "With this man, there is nothing at the moment that links him directly" to the conspiracy, he said. Other officials said investigators were still trying to determine whether the man had contact with the bombers while he was in the country.

Sept. 2004 - Pakistan's Most Wanted Terrorists

MSNBC - Police Hunt 5th Man Seen at Luton Station
The hunt for the man who spoke with the bombers began after British intelligence reviewed a surveillance video from Luton rail station north of London and saw the four attackers huddled in conversation with another man on the morning of the bombings, British and U.S. intelligence sources said Friday.

British intelligence has interviewed a witness who was at the station at the time, according to the sources, who could discuss intelligence matters only on condition of anonymity. The witness told authorities that when the conversation among the men ended, the four now identified as the bombers walked away together, while the other, still-unidentified man left alone in the opposite direction and boarded a train.

The report on private radio station Cadena Ser quoted security sources as saying the components may point to the bomb having been set by an extremist Islamic group such as al Qaeda.  The bombs, which blew up on four trains, were in backpacks and activated by mobile telephones that had had their alarms set for 7:39am (01:39am EST) Thursday.

The detonator in the unexploded bomb recovered by police contained a copper detonator whereas the detonators commonly used by ETA are made of aluminum, the report said.

The backpack examined by investigators was picked up from one of the mangled trains and put together with other lost luggage after the blasts. It was later found to contain an unexploded bomb, which police defused, according to the report. The backpack contained 10.2 kg (22 pounds) of Spanish-made plastic explosives and about one kg of screws and nails. The detonator was also Spanish-made.

NEW YORK July 18, 2005 (Reuters) - Britain's top intelligence and law enforcement officials concluded less than a month before the London bombings that there was no group with current intent and the capability to attack the U.K., the New York Times reported on Tuesday, citing a confidential intelligence report.

The Times said authorities made their conclusion in the wake of a terror threat assessment by the Joint Terrorist Analysis Center, which includes officials from Britain's top intelligence agencies, as well as Customs and the Metropolitan Police.

The assessment, according to the newspaper, prompted the British government to lower its formal threat assessment one level, from "severe defined" to "substantial." Asked to comment on the document, a senior British official, who spoke on condition of anonymity, said according to the newspaper, "We do not discuss intelligence assessments."

CAIRO July 19, 2005 (Reuters) -- British authorities are sure that an Egyptian biochemist being questioned in Egypt had no role in the London bombings, a state-owned Egyptian newspaper said today, quoting a senior security official.

"There is complete security cooperation with the British side, which is convinced from the questioning carried out by Egypt, that Elnashar had no role in these explosions," al-Ahram newspaper quoted the security source as saying.

Chemist Has 'No Links' With Al Qaeda

Egyptian biochemist Magdy Mahmoud el-Nashar  

LUTON, England July 18, 2005 (AFP) -- In a Muslim district of Luton, where the four suspected London bombers met on the morning of July 7, all agreed the attacks were wrong, but were quick to point to the Iraq war as an explanation for them. Muslims, most of them originally from Bangladesh and Pakistan, make up 14.5 percent of Luton's 180,000 inhabitants.

Although few people in the neighbourhood voiced extreme views, all had harsh words for US President George W. Bush and British Prime Minister Tony Blair.

"Bush and Blair, they are not caring about the people in Iraq, about the innocent people getting killed," said Abdul Mohammed, 45, a Sunni Muslim from Bangladesh who settled in Britain 29 years ago. He felt his religion to be under attack by Western powers. "Since the last 10 years, they are trying to control everything all over the world ... Islam is attacked: in Iraq, in Afghanistan, in Palestine," argued the father of four.

Dublin July 14, 2005 (Irish Examiner) -- THE BALKANS were last night being named as the possible source of the explosive material used in the London bombings.

French Interior Minister Nicolas Sarkozy told the emergency meeting of EU justice ministers in Brussels, that there was strong suspicion the explosives used in the bombings came from the Balkans or Eastern Europe, where it is possible to buy the material on the black market after the Balkan wars.

However, British Home Secretary Charles Clarke said he was bewildered by the comments.

Determining the origin of the explosives is vital and investigators believe one man assembled all four devices. Initial forensic investigations suggest each device used in the attack had less than 10 pounds (4.5kg) of explosive, a quantity small enough to have been hidden in a rucksack.

Traces of military plastic explosive, more deadly and efficient than commercial varieties is understood to have been found in the debris of the wrecked Underground carriages and the bus.

Scotland Yard has asked its counterparts around Europe to check stockpiles at military bases and building sites for missing explosives. Military explosive is hard to detect even by trained sniffer dogs, easy to hide, and stable if smuggled across a European border and then into Britain in a container.

Superintendent Christophe Chaboud, head of the French security service's Anti-terrorist Co-ordination Unit, said: "The use of military explosives is very worrying. We are more used to seeing home-made explosives, made from chemicals. How did they procure them? Either they were supplied by the underground market, for example from the Balkans, or they benefited from accomplices who removed explosives from a military base."

After intensive efforts, availability of Semtex [1] used extensively by the Provisional IRA, has dried up. However, there are a number of alternatives, notably C4, which comes in sticks and can be moulded into a shape suitable for a bomb. C4 is a high-quality plastic explosive that has been used by al-Qaida-affiliated terrorists in other attacks.

The explosive is manufactured mainly in the US but there is evidence that military explosives have been bought by terrorist groups from sources in Croatia and elsewhere in the Balkans. Islamic militants are reported to have obtained military explosives from Belgrade in recent years.

USS Cole - attack with C4 explosives

[1] Semtex   It is generally believed that the IRA still has at least 2.5 tonnes of Semtex with a shelf life of perhaps another 20 years.

By Craig Whitlock and Kamran Khan  ::  Washington Post

7/19/2005 LONDON - One of the suspected London transit bombers visited Israel for a day in the spring of 2003, Israeli authorities have reported as part of an international effort to re-create the travels of the four men who investigators believe set off the July 7 explosions.

Mohammed Sidique Khan arrived in Tel Aviv and left the next day, senior Israeli intelligence officials have told Israeli reporters. Investigators say they have found no evidence that his trip was related to the subsequent April 30, 2003, suicide attack on a Tel Aviv cafe by two British men of Pakistani origin.  

The purpose of Khan's trip to Israel is one of the many unknowns in the 10-day-old investigation.

Several weeks after his visit, a British-born man of Pakistani descent, Asif Hanif, blew himself up at Mike's Place, a Tel Aviv nightspot, killing three other people. Two weeks later, the body of another British citizen, Omar Sharif, who investigators said fled the bar after a bomb he was carrying failed to detonate, was found in the sea off Tel Aviv.

Avi Tabib - Hero of Mike's Place

[...]
New details emerged Monday on trips that three of the four suspects made to Pakistan before the attacks. Khan and Shehzad Tanweer arrived in Karachi, Pakistan's largest city, on Nov. 16 last year on the same Turkish Airlines flight, then flew home together Feb. 7, Pakistani investigators said after reviewing immigration records.

A third suspect, Husib Mir Hussain, flew into Karachi on July 15, 2004, on a Saudi Arabian Airlines flight from Riyadh, records show. Pakistani officials said they did not know how long Hussain stayed, his family in Leeds told British investigators that he was gone for about four months.