The last four British men held as terrorism suspects at Guantanamo Bay have arrived back in the UK, after almost three years in US custody.
The men, one from Birmingham and three from London, were held after the US accused them of having al-Qaeda links.
The RAF C-17 plane carrying Moazzam Begg, Martin Mubanga, Richard Belmar and Feroz Abbasi landed at RAF Northolt in west London at about 1700 GMT.
They were arrested on arrival and taken to Paddington Green police station.
Protests are taking place outside the high-security station where the men are now being held, but police say they have to investigate why the four were originally detained.
He has been keeping all the pain and suffering from me
Azmat Begg
The Pentagon has said they were freed after a request from the British government, which had promised “that the detainees will not pose a continuing security threat to the United States or its allies”.
The men’s flight home was filmed by police officers and was joined by two independent observers, including one Muslim.
After landing, a police van was driven onto the plane and later left the base, taking the men to the central London police station.
Groups of protesters chanting and waving placards were outside the station when the men arrived shortly before 1840 GMT.
Some said the police were “giving negative feedback to the Muslim community and the wider community”.
The Muslim Safety Forum, set up after the 11 September attacks, said it had asked the men be allowed to return home while the police carried out their investigation.
It said arresting them seemed like a political decision.
Massoud Shadjareh, from the organisation, said: “What sort of homecoming is this? They are innocent people.”
Scotland Yard’s Deputy Assistant Commissioner Peter Clarke said officers had talked to Muslim representatives and knew there were strong feelings about the case.
But he said: “The fact is that we have an absolute duty on behalf of all communities to investigate the circumstances leading to the men’s detention.”
He added: “We are totally committed to ensuring that the men are treated properly and fairly.”
The men were arrested under Section 41 of the Terrorism Act 2000, covering alleged involvement in the commission, preparation or instigation of acts of terrorism.
They will be checked by a police doctor to see if they are fit to be detained and interviewed by anti-terrorism branch officers.
However it is likely they will not be questioned until Wednesday, said BBC correspondent Daniel Sandford.
They will be allowed a phone call, access to a lawyer and, “due to the unique circumstances”, they will be allowed to see a relative, the spokesman said.
If the UK isn’t going to make representations on their behalf, who is?
Amnesty International
Mr Begg’s father Azmat, who at one stage thought his son would face the death penalty when he was selected for a military tribunal hearing, watched television pictures of the arrival from Birmingham.
“It is a great relief for me,” he said. “I am a little bit nervous and emotional.”
Five other British detainees were freed from Guantanamo last year and were released without charge after questioning by police in the UK.
Some later said they had been hooded and shackled to the floor in painful stress positions, and had witnessed beatings and other abuse during their time at Guantanamo.
BBC home affairs correspondent Danny Shaw said alleged evidence against the men “may well have been obtained in circumstances not acceptable in courts here, perhaps under duress or perhaps from the battlefields in Afghanistan and so on”.
Washington has alleged that all four men trained at camps run by al-Qaeda.
They were among hundreds of foreign nationals detained by the US without trial in the wake of the 11 September attacks.