Former pop star Cat Stevens was being returned to Britain after being branded a terrorist supporter and thrown out of the United States.
The musician, who converted to Islam and changed his name to Yusuf Islam in the 1970s, was detained and questioned by the FBI after his Washington-bound flight was diverted on Tuesday.
He had been travelling with his 21-year-old daughter Maymanah, who was allowed into the country after the flight had eventually continued to Washington's Dulles Airport.
But the move to deport him sparked a protest to the US government by Foreign Secretary Jack Straw and angered Muslim groups on both sides of the Atlantic.
Islam's brother David Gordon, said Islam had condemned terrorist acts and donated money to terrorism victims.
"He just wants to be an ambassador for peace," said Gordon, who lives in Princeton, New Jersey, and serves as Islam's business manager.
US security sources confirmed that Islam, 56, who has mingled at charity events with Prime Minister Tony Blair and the Prince of Wales, was expected to arrive in London.
Officials refused to give further details about his deportation.
Straw told US secretary of state Colin Powell that the action "should not have been taken".
A spokesman for Straw said: "He (Straw) heard the reports of the incident involving Cat Stevens.
"He did say to the secretary of state that this action should not have been taken."
Straw was in New York where he was to address the United Nations General Assembly.
US security officials said Islam's name was on a security watch list.
The discovery, after United Airlines Flight 919 had already taken off, led to the aircraft being diverted 1,000km to Bangor, Maine.
After being escorted off the aircraft and questioned by the FBI, Islam was denied entry to the US on national security grounds.
The Department of Homeland Security said Islam was put on the watch list "because of concerns that about activities that could potentially be related to terrorism".
"The intelligence community has come into possession of additional information that raises concerns about him," a spokesman said.
US government sources claimed that Islam had financially supported the terrorist group Hamas.
He was denied entry to Israel four years ago amid reports that he had given tens of thousands of dollars to Hamas.
At the time, Islam strongly denied knowingly giving money to terrorists.
British officials, speaking anonymously, said there was no evidence in the British intelligence community that Islam posed any danger.
That revelation is sure to prompt further anger among Muslim groups on both sides of the Atlantic, who believe Islam was targeted simply because of his faith.
Islam has spoken out against the Russian school massacre and the September 11 terror attacks.
After September 11, he said: "No right-thinking follower of Islam could possibly condone such an action."
He is head of the Islamia Schools trust and has met the prime minister, the Prince of Wales and Home Secretary David Blunkett in that capacity.
Islam has also founded a charity raising money for orphans and families afflicted by war in areas such as Kosovo, Bosnia, and Iraq.
The refusal to allow Islam into the US on national security grounds was described by the Muslim Council of Britain as a "slap in the face of sanity".
Deputy general secretary, Mohammad Abdul Bari, described Islam as "a very moderate man".
"He is very well respected in the Muslim community," he said.
"We are really appalled at what is happening. It is a slap in the face of sanity. If prominent, well-known personalities are treated like this, then how can there be bridge building?"
A spokesman for Islamia Schools said: "Everyone who has heard the news has been pretty sympathetic. He is more famed now as a peace activist than he was as a singer."
The Muslim Association of Britain condemned the decision by the US authorities, which followed a move last month to prevent an Islamic professor taking up a teaching post in America.
Spokesman Anas Altikriti said such actions prevented "open, constructive and positive dialogue" between the US and Muslims around the world.
He added: "It seems that the US officials would rather that the untrue and distorted images of Islam and Muslims persist in the minds of its own citizens."
In Washington, the US Council on American-Islamic Relations also attacked the treatment of Islam.
"When internationally-respected Islamic personalities like Yusuf Islam .. are denied entry to the United States, it sends the disturbing message that even moderate and mainstream Muslims will now be treated like terrorists," said Nihad Awad, the group's executive director.
Cat Stevens had a string of hits in the 1960s and 1970s, including Wild World and Morning Has Broken, but abandoned his music career and his name in the late 1970s.
Last year he released two songs, including a re-recording of his 1970s hit Peace Train, to express his opposition to the war in Iraq.
Islam appears to have been a recent addition to the security watch list.
He travelled to the US unhindered in May for a charity event and to promote a DVD of his 1976 MajiKat tour
Cat Stevens' treatment angers UK
BRITISH Foreign Secretary Jack Straw has complained to his American counterpart Colin Powell about the deportation from the US of former pop star Cat Stevens as a possible terrorist risk.
Mr Straw, in New York for United Nations meetings, had spoken to the US Secretary of State about the imminent removal of the British musician, his spokesman said.
"He heard the reports of the incident involving Cat Stevens," the spokesman said. "He did say to the Secretary of State that this action should not have been taken."
Stevens, who sold many millions of records before abandoning his pop career when he became a Muslim in the late 1970s, changing his name to Yusuf Islam.
He was due to be sent back to Britain later today.
Yesterday, a United Airlines flight from London to Washington was diverted to Bangor, Maine, after US authorities discovered that Islam was aboard.
His name appeared on several terrorism "watch lists" and he was rejected entry by US authorities.
"Why is he on the watch lists? Because of his activities that could be potentially linked to terrorism," US Homeland Security spokesman Brian Doyle said yesterday.
"The intelligence community has come into possession of additional information that further raises our concern."
Mr Islam was denied entry to Israel in 2000 over suspicions that he had given money to the radical Palestinian group Hamas. The singer has consistently denied supporting terrorism.
But unnamed British officials claim there is no evidence known to the country's intelligence services that the former singer posed any danger.
The decision was also slammed as divisive by Islamic groups in Britain.
Mr Islam, who has been a vocal campaigner for the establishment of faith-based Muslim schools in Britain, was "a very moderate man", the Muslim Council of Britain's deputy general secretary, Mohammad Abdul Bari, said.
"We are really appalled at what is happening," said Bari, who later held talks on the issue with junior foreign office minister Douglas Alexander.
"It is a slap in the face of sanity. If prominent, well-known personalities are treated like this, then how can there be bridge building?"
A statement released through the singer's website also expressed amazement at the US stance.
"What we can say ... is that he will be shocked and angered at being associated with anyone who commits acts of violence," it read.
"He has vehemently and consistently criticized terrorist acts and has always advocated peace through his songs and his extensive humanitarian relief work.
"Any suggestion therefore that he poses a security risk due to alleged connections with terrorist activities is totally denied as it is simply wrong."
The Muslim Association of Britain, another leading Islamic group, also condemned the decision, saying it followed a move last month to prevent an Islamic professor taking up a teaching post in the US.
Spokesman Anas Altikriti said such actions prevented "open, constructive and positive dialogue" between the United States and Muslims around the world.
"It seems that the US officials would rather that the untrue and distorted images of Islam and Muslims persist in the minds of its own citizens," he said.
AG: Slam for that paranoid move policy. Everything that have a beard will now labeling as a terror by that moron FBI. What a poor rabbi now also can't fly.