ONE of the London suicide bombers was allowed to tour the Houses of Parliament as the guest of an MP months after police and intelligence services became aware of his links to another alleged bomb plot, it emerged last night.
Mohammad Sidique Khan, 30, was a guest of the Labour MP Jon Trickett in July 2004, four months after he had been identified by intelligence officials as a "criminal associate" of one of the subjects of a major counter-terrorism operation that had resulted in several arrests.
The extraordinary visit emerged as an Egyptian biochemist who may be linked to the bombers was arrested in Cairo, where he was due to be questioned by Scotland Yard detectives.
The astonishing revelation about the killer's Commons visit throws into question previous assertions that none of the bombers was known to police in connection with terrorist allegations and comes amid growing concerns about how the bombers were allowed to strike.
Britain's "slack" border controls were already in the spotlight after it became clear that a significant al-Qaeda suspect had entered the country undetected and slipped away again hours before the London suicide attacks, which claimed the lives of 54 people.
The suspected terrorist was not put under surveillance after entering Britain, but is now being urgently sought by the intelligence services in connection with the bomb blasts.
The revelation - which came as police warned that another attack was "a strong possibility" - prompted calls from opposition parties and immigration staff for tighter controls on people entering and leaving Britain, and raised questions about security precautions before the London attacks.
Downing Street indicated yesterday that an internal investigation was being carried out into whether mistakes were made in the run-up to the attacks. A spokesman for the Prime Minister said: "We are going to let the investigation take its course. We are going to let the review mechanisms take their course, and we will do this properly."
Doubts have also been raised about why the Joint Terrorism Assessment Centre had relaxed the terrorist threat status from "severe general" down to "substantial" before the attacks.
There was, however, some good news for police and intelligence services yesterday as the Egyptian biochemist sought in connection with the attacks was arrested in Cairo. Magdy Mahmoud Mustafa el-Nashar, 33, who until recently had been teaching chemistry at Leeds University, was being questioned last night by Egyptian authorities. El-Nashar is thought to have rented one of the homes police searched in Leeds in a series of raids on Tuesday.
El-Nashar is said to have told the authorities that he arrived on holiday about two weeks ago and had intended to go back to Britain to continue his studies.
Police are still hunting the man who is believed to have masterminded the attacks, and the Metropolitan Police commissioner, Sir Ian Blair, said he was convinced that a link between the attackers and al-Qaeda would soon emerge.
"What we expect to find at some stage is that there is a clear al-Qaeda link, a clear al-Qaeda approach, because the four men who are dead, who we believe are the bombers, are in the category of foot soldiers," he said.
Pakistani intelligence officials are looking into a connection between one of the three Britons and two al-Qaeda-linked militant groups in that country. They confirmed that Shahzad Tanweer spent four or five days at a complex run by the terrorist group Lashkar-e-Taiba - as first reported by The Scotsman - and said he also met a member of another al-Qaeda-linked Pakistani terrorist group who was later arrested for bombing a church in Islamabad.
More details emerged yesterday that there had been indications an attack was imminent. Plans for attacks on targets in both the United States and Britain were discovered among material found during the capture of Abu Faraj Farj al-Liby, one of the most senior al-Qaeda leaders, and of a Pakistani computer expert, Mohammad Naeem Noor Khan. Some intelligence officials said those plans included attacks on London's transport system, as well as Heathrow Airport.
Last night, the Labour Party released more details about the Westminster visit by Khan, who killed himself and six commuters in the Edgware Road Tube blast. He had been invited in his capacity as a learning mentor at Hillside Primary School in Beeston, Leeds, where Mr Tickett's wife, Sarah, is the headteacher.
Mr Trickett's son was in the same school year group as Khan 17 years ago, and Khan had visited Mr Trickett and his wife at their home.
In July last year, the Hemsworth MP's wife took a number of her pupils on a trip to London and Khan accompanied the party as a member of school staff. The Labour Party said the group visited a number of attractions, including the London Eye and St James's Park.
During the visit, the Leeds Central MP, Hilary Benn, the International Development Secretary, joined the group in Portcullis House to talk about his role as their local MP.
They then met Mr Trickett, who used to represent Beeston on Leeds City Council, and who accompanied the group on the rest of their visit around the Palace of Westminster.
It also emerged yesterday that Farida Patel, Khan's mother-in-law, was pictured at a Buckingham Palace garden party with her husband, Abdul Aslam, and their daughter, Hasina. In 1998, she became the first Asian woman to attend a Palace garden party. Yesterday, she was being guarded by police in a safe house as forensic detectives continued to comb her home for clues.