Egyptian police hold scientist who lived in Leeds

Magdi Mahmoud el-Nashar, 33, who completed a PhD at Leeds University this year, has been linked to several of the suicide bombers and is to be questioned by anti-terrorist and MI5 officers.

Detectives are trying to establish who made the bombs. Forensic analysis has revealed that the explosive used was a home-made substance nicknamed "Mother of Satan", which has been used in previous al-Qa'ida attacks.

Mr El-Nashar, who left his home in Leeds shortly before the bombings, denies any wrongdoing.

News of his arrest by the Egyptian authorities came as the head of the Metropolitan Police said that a known al-Qa'ida suspect had travelled into Britain and left the day before the attack. The suspected terrorist spent about two weeks in Britain, but Sir Ian Blair, the Commissioner of the Metropolitan Police, said there was no evidence he made any contact with the four bombers.He also said that the security services had not monitored him while in the UK because he was considered very low risk.

One authoritative source said, however, that it now appeared that no al-Qa'ida member had entered the UK during that period and the report was based on a misunderstanding.

Sir Ian said that, having found the four suicide bombers - three of whom lived in the Leeds area and the fourth in Aylesbury, Buckinghamshire - the police were concentrating on the rest of the terror team.

He said: "What we expect to find at some stage, is that there is a clear al-Qa'ida link, a clear al-Qa'ida approach, because the four men who are dead, who we believe are the bombers, are in the category of foot soldiers.

"So, therefore, what we have got to find is who encouraged them, who trained them, who is the chemist? Those are the things in which we are now interested."

Mr El-Nashar, who left Britain three days before the London attacks, will be questioned about any contacts he had with the four bombers and access to the property in Leeds that was used to make the bombs.

Leeds University said Mr El-Nashar, who is thought to have been close to the suicide bomber Lindsay Jermalne, came to Leeds to study for a PhD in the school of biochemistry in October 2000. His subject was "Development of a novel matrix for the immobilisation of enzymes for biotechnology" and he was sponsored by the National Research Centre in Cairo.

He was awarded his PhD on 6 May this year, although he did not attend the graduation ceremony. His request to study for a teaching qualification was rejected. He was also awarded a £30,000 research grant by the Yorkshire Forward regional development agency, although did not use it.

An employee at Leeds University said that Mr ElNashar's books and papers at the university had been left as if he was destined to return for the next academic year. Professor John Findlay, Professor of Biochemistry, said: "I've had contact with him. For me he was fine - nothing abnormal in any way."

The significance of the arrest was unclear last night. Scotland Yard had initially considered him a low-level suspect, and he is not a known al-Qa'ida supporter or on MI5's list of terror suspects.

A counter-terrorism source said: "This man is of interest to us. He is a chemistry student who was living near the bombers in Leeds and he disappeared abroad shortly before the bombings. But until we have interviewed him and looked into his background we will not know how significant he is."

George Thompson, 57, who lives opposite the flat that Mr El-Nashar is said to have allowed some of the bombers access, said yesterday that he had seen the biochemist with two young boys, whom he took to be his sons, and a female member of the household who wore a hijab. He seemed ike any other resident, gardening and holding occasional barbecues at the property. Then, two years ago, the scientists appeared to have sub-let the flat after which "people came and went".

Mr Thompson said: "It seemed as though [the visitors] didn't want to be seen. They came at night or as soon as it got darkish."

Two of the men he had seen were probably among those now known to be suicide bombers, Mr Thompson said. They would arrive as late as 10pm, sometimes staying overnight and other times leaving in the early hours.