The Times has learnt that officials at the British High Commission in Islamabad have already taken the first steps to secure the return of Mr Rauf, 25, who is from Birmingham. Scotland Yard officers have flown to Islamabad and, if the extradition process moves quickly, will be on hand to escort him on a private flight to Britain. The moves coincided yesterday with the arrest of another suspect as the scope of Operation Overt, the police inquiry into the alleged airline plot, continued to widen. The latest arrest brings to 24 the number of people in custody at three London police stations. At least one, Cosser Ali, 24, is female.

Scotland Yard will return to City of Westminster Magistrates’ Court today to seek further time to question the suspects arrested last Thursday. The court can grant police up to 28 days before the suspects must be charged or released.

This is the first time that the extended detention period has been available to the Anti-Terrorist Branch. Senior officers are expected to use it to its full extent before bringing charges.

In Pakistan, the authorities have indicated that they will look favourably on any request to extradite Mr Rauf. He left for Pakistan in April 2002 after the murder of his uncle, Mohammed Saeed, 45. Mr Rauf’s brother, Tayib, 21, is one of more than 20 people arrested in anti-terrorist raids last week in London, Birmingham and High Wycombe.

Britain has no formal extradition agreement with Pakistan but there are international treaties and ad hoc arrangements under which Mr Rauf could be returned.

Scotland Yard said that the new suspect was picked up in the Thames Valley Constabulary area. Since the operation began a week ago tonight, 46 raids have been carried out on on business and residential premises.

The searches are so painstaking and extensive, involving almost every specialist scenes-of-crime team in southern England, that 23 premises are still being examined. The largest operation is continuing in an area of woodland in High Wycombe where it has been reported that bomb-making chemicals have been found.

Police have also seized 20 vehicles which are being subjected to detailed forensic science examination. Police sources said that the process of accumulating evidence from overseas and extracting information from computer hard drives was extremely time-consuming.

Dozens of computers have been seized from suspects’ homes and from internet cafés that had been under surveillance for months before the arrests.

Amjad Sarwar, the brother of one of those in custody, told Channel 4 News last night that his family had no connections with terrorism. He said that his brother Assad had dropped out of university and become devoutly religious.

Mr Sarwar said: “They have got it all wrong. He is an innocent guy. He minds his own business; he’s been helping the youth out considerably in the area and he’s got nothing to do with it. There is no way he could have anything to do with terrorism.”

The international dimension of the inquiry will be reflected this morning when John Reid, the Home Secretary, briefs the French and German interior ministers on its extent and progress. The Times has reported that extensive inquiries are being made in Germany into alleged links between a British suspect and a fugitive member of the Hamburg cell that planned attacks in the US on September 11, 2001.

The first step in seeking Mr Rauf’s return was the sending by the high commission of a diplomatic request to the Pakistani Foreign Affairs Ministry asking whether he was a British citizen or held dual nationality.

Tasnim Aslam, of the Foreign Ministry, said: “We do not have any extradition treaty at the moment but yes, because he is a British national, the possibility of his extradition remains there.”

A spokeswoman for the Home Office said: “There is no current bilateral extradition treaty with Pakistan. However, there are a number of international conventions, such as the Convention for the Suppression of Terrorist Bombings, that set up formal extradition arrangements for certain types of criminal conduct.”

Times Recommends

• PM to sue Icesave to get savers' money
• Former UBS lawyer pays $6.5m to settle probe
• Test case over non-dom told to pay UK taxes