A fourth suspect in the London bombings of July 21st was last night being held in a Rome cell, after being arrested by Italian police following an operation stretching across three countries.
Italian interior minister Giuseppe Pisanu named the suspect as Hussain Osman (27) - a Somali-born naturalised British subject.
Rome's chief anti-terrorist prosecutor, Franco Ionta, was last night questioning the suspect. Police sources said he had been detained on a warrant issued by a British court.
Italian media reports said Mr Osman was suspected of the failed attack at Shepherd's Bush. This would identify him with the man caught on CCTV at Westbourne Park station.
According to initial reports, Mr Osman was arrested in the Centocelle area of Rome. Italian news reports quoted police sources as saying he had been traced to the Italian capital by the mobile phone he was using.
The phone, belonging to a relative who lives in Rome, was understood to have been used on July 21st at one of the locations linked to the bombings. The relative was variously identified as Mr Osman's brother and brother-in-law.
According to one report, the suspect left London on Wednesday. Police monitored the phone in London, Paris, Milan and finally Rome. According to the RAI TV network, Mr Osman was holding the phone in his hand when police burst in on him late yesterday afternoon. He was said not have resisted arrest.
Rome's prefect, Achille Serra, said last night the operation was "the result of splendid co-operation between Rome and London".
But the news that Mr Osman had slipped across at least two international borders also prompted renewed calls in Italy for the scrapping of the EU's Schengen agreement, which creates open borders between states.
Roberto Calderoli, a minister in Silvio Berlusconi's conservative coalition cabinet, said: "If the necessary controls had been carried out then this individual would have been stopped at the frontier."
Police said last night that further searches were being carried out in Rome, but they did not believe yesterday's arrest was linked with any potential terrorist action in Italy.