Its members, dressed in smart suits, bow ties and dark glasses, believe that they can only achieve "freedom" by completely dissociating black people from white.
The movement was founded in the early 1930s by Fard Muhammed, who preached to the black community of Detroit about Islam, their "pre-slavery religion".
The Nation then expanded under Fard's officer, Elijah Muhammad, and later with Malcolm X as its chief spokesman until he was expelled from the movement for commenting on the killing of President Kennedy.
But it is under the firebrand leadership of the Rev Louis Farrakhan that the Nation of Islam has provoked most criticism.
Mr Farrakhan, to whom the British section defers as leader, has prompted outraged condemnation for his attacks on white people and particularly Jews and homosexuals, as part of his message of self-empowerment and self- help for blacks.
As a result of objections from the Board of Deputies of British Jews, Mr Farrakhan has been banned from entering Britain for the past 13 years, although that is currently under review.
His work was taken up by a handful of black "brothers" who saw him preaching on television in 1986.
They travelled to Chicago to meet him and returned to found the first British Nation of Islam mosque in Brixton, south London.
Among their more controversial recruitment drives was a rally held by their leader, Wayne X, on the Broadwater Farm estate, the scene of some of Britain's worst race riots.
Recently they were among those who brought new fire to Speaker's Corner in Hyde Park with their black separatist message.
In pockets across London, in Goldhawk Road in the west, Brixton to the south, east in Stoke Newington and north in Harlesden and Tottenham, they can be seen most weeks selling their newspaper.
Despite the controversy and criticism from more orthodox Muslims in Britain, members of the movement have also been involved in constructive social welfare programmes designed to reduce crime and drugs. No-smoking, no- drinking Nation members visit jails and have a good record of transforming inmates into law-abiding citizens.
There is an arch-conservative insistence on family values and they are a visible presence at any black funeral of note.
However, Maurice Mcleod, political editor of The Voice black newspaper, said the reaction of the black community to the Nation of Islam was mixed.
Despite the popularity of some parts of its message, separation from the white population was viewed as being neither practical nor desirable.
"They do a lot of ground- roots work in the community. They appeal to working-class black people who like to dress smartly and have respect. But I don't think there's thousands of black people joining."
Although they shun the white media, neither do they speak much to the black press either.
Mr Mcleod said it was difficult to gauge exactly how many of them there were and what they believed.
They always denied anti-Semitism on the rare occasions they talked to him.