The Investigation

Sarah Challands, CTV.ca News

On Thursday, July 7, London was plunged into chaos after four suicide bombers struck during the morning rush hour.

Three bombs went off on underground trains while another destroyed a double-decker bus. The bombs killed 52 innocent people and injured 700.

Exactly two weeks later on Thursday, July 21, four attempted bombings took place in the capital, but the devices failed to explode.

Once again three were on underground trains and one on a bus.

Although nobody was injured, British police confirmed that the bombs were designed to kill.

More than 3,000 witness statements have been gathered and 80,000 video tapes analyzed.

So far nobody has been charged in connection with the bombings and British police had voiced fears that the investigation has been superceded by the inquiry into the failed blasts on July 21.

With the four perpetrators dead, inquiries have focused on attempting to identify and trace members of a support network which assisted the bombers in financing and preparing the attacks.

It is considered unlikely that the four men were acting alone. They had all visited Pakistan in the run-up to the attack and a video showing one of the bombers -- Mohammed Sidique Khan, which was recorded up to a year before the blasts -- was broadcast in September.

Video

The first breakthrough in the investigation came after a review of security video taken at train stations on the morning of July 7.

Images from surveillance cameras enabled investigators to provide a timeline of the horrifying events unleashed on Londoners during the morning rush hour:

• 8:30: Four young men, chatting casually and each wearing a backpack, entered Luton train station (about 30 minutes north of London). They moved off in separate directions.
• 8:50: Three explosions occur almost simultaneously on three London Underground trains: between Aldgate and Liverpool Street stations on the Circle Line; between Russell Square and King's Cross stations on the Piccadilly Line; and at Edgware Road station on the Circle Line.
• 9:47: A number 30 double-decker bus near Tavistock Square is destroyed by a fourth explosion.

Practice run

Other video footage shows the bombers staged a practice run nine days before the attack.

The images show three of the bombers entering Luton station on June 28, before travelling to King's Cross station where they are also pictured.

The three, Mohammad Sidique Khan, Shehzad Tanweer and Germaine Lindsay, were conducting a carefully planned reconnaissance exercise, police said.

Deputy Assistant Commissioner Peter Clarke, head of Scotland Yard's Anti-Terrorist Branch, said it was "part of a terrorist's methodology" to check timings, lay-out and security precautions.

Evidence of a dummy run supports the theory that all four had planned to detonate their rucksack bombs on the Underground system.

It is believed that the bus bomber, Hasib Hussain, was prevented from getting onto the Northern Line on the day of the attacks because the service had been disrupted.

Police traced the movements after recovering tickets and receipts from houses connected to the bombers which pointed to their trip.

Police also revealed that two bombs were found in a car left by the attackers at Luton train station on July 7.

Al-Qaeda

Meanwhile, Al-Qaeda’s deputy leader has admitted that the July 7 bombings were carried out by the group.

In a videotaped message aired on Arab television station al-Jazeera in September, Ayman al-Zawahri said al-Qaeda had the "honour" of carrying out the attacks.

Zawahri said the "blessed" London attacks were targeted at "the British Crusader's arrogance and against the American Crusader's aggression on the Islamic nation for 100 years".

Explosives

Police haven't yet identified precisely the type of bomb used in the London attacks.

But a London newspaper reported that traces of C4 -- a technically-advanced plastic explosive -- were found at all four blast sites.

C4, manufactured mostly in the U.S., is considered more deadly and efficient than commercial explosives, and is difficult to obtain in the United Kingdom. Some have speculated that the explosive material used in the attacks was smuggled into Britain by an individual or group. Investigators didn’t find any timer components or detonators.

London police said they found significant quantities of explosives in one house in the Burley neighborhood of Leeds.

Media reports, citing unnamed police sources, described the find as a "bomb factory."

Pakistan

The hunt for those connected to recruiting, financing and supplying the four suicide bombers continues.

Pakistani officials confirmed that three of the four bombers visited the country last year. Their movements were tracked by the Personal Identification and Evaluation System (Pisces), which takes photos of everyone entering Pakistan.

Their reports reveal:

• Khan and Tanweer spent three months in Pakistan in 2004. They flew into Karachi together in November and left together in February 2005.
• Authorities in Islamabad said they questioned students, teachers and administrators at one of two religious schools they say Tanweer visited.
• Authorities were examining a possible connection between Tanweer and two al-Qaeda-linked militant groups.
• Hussain flew to Pakistan last July, although it's not clear how long he stayed.

Police leads

An earlier claim by British security officials that the four attackers were unknown to them was contradicted by an official admission on July 17 when officials revealed that at least one of the bombers – Khan -- was known to British intelligence before the attacks.

And FBI reports revealed that U.S. intelligence had warned that Lindsay, the fourth bomber who died in the worst of the attacks, was on a terror watch list, but Britain's MI5 had failed to monitor him.

A man who identified himself as Lindsay's father told local Jamaican radio RJR that he had not seen his son since the boy visited when he was 11. The two began conversing weekly over the phone in 2004, and the younger Lindsay confided that be had become a Muslim.

Magdy el-Nashar, an Egyptian-born chemist and lecturer at Leeds University who rented the house where explosives were found, was arrested in Cairo on July 15.

He was released several weeks later after being cleared of having had any connection with the attacks. He is not believed to have returned to the UK.

A number of other men thought to have links with the four bombers in Leeds have since disappeared.

Several police searches of homes, shops and other premises across the U.K. have failed to bring any arrests.

Bus

On October 3, a new bus was unveiled to replace the one destroyed at Tavistock Square.

London mayor Ken Livingstone said the bus was named Spirit of London as a tribute to the 13 people who died.

Livingstone said he hoped George Psaradakis, the driver on July 7, would take the wheel.

Compensation

Meanwhile, the Criminal Injuries Compensation Authority said on October 4 that the first payments had been made to victims of the bombings,

A dedicated team is dealing with compensation for bereaved relatives and the severely injured.

Final figures will be calculated when the extent of injuries and financial loss are clear, which may take "some time", according to CICA.