And right now it is defining Marc too. In a couple of days this Los Angeles-based freelance sound man will be working on a homes and garden show. But today, he is in Minister Louis Farrakhan's suite wondering what to do with the microphone. Ordinarily, in a briefly intrusive, intimate moment, he would clip it on an interviewee's shirt. But this is no ordinary situation.

In his eyeline are the broad chests and bow-ties of Farrakhan's bodyguards. They will take a bullet for their boss; they will not take any nonsense around him. Take a step closer than is necessary towards Farrakhan and they will take a step closer than is comfortable towards you. The night before we had all been thrown out of a banquet dedicated to the first family - Farrakhan's family. An official had asked me to stand in a certain place and I had asked why. We were out on the street before you could say "separate but equal". Now we are in Farrakhan's suite, waiting for him to arrive. One of the minders takes the microphone from Marc and says he will put it on. Then, in walks Farrakhan, tall, erect, bespectacled. His skin is smooth caramel, his suit only slightly darker and there is little evidence of his 70 years in his face or his gait. The room bristles, not with excitement, but with a mixture of reverence and obsequiousness. Big men suddenly made small in the presence of the largest man they can imagine.

Only when he takes his chair does it become apparent that whoever has taken the microphone from Marc does not know what to do with it. Farrakhan looks up, slightly exasperated but completely composed. "Whose responsibility is this?" he asks. His voice is a velvet purr, his mouth a lus trous smile. Marc tentatively raises his hand.

"Well don't be afraid," says Farrakhan. The former calypso singer who once went by the name of the Charmer. "Come here and put it on. I'm not going to hurt you."

Farrakhan is very believable. In fact, for the leader of an organisation which believes, among other things, that white people were made out of germs by a mad scientist and were originally born with tails, he is unbelievably believable. Others who have interviewed him recall how his charm can dissolve into rage when pressed on certain matters. He has been known to occasionally descend into a babble of conspiracy theories and numerology. "That number 19," he told a bemused crowd at the Million Man March in 1995. "When you have a nine you have a womb that is pregnant. And when you have a one standing by the nine it means that there's something secret that has to be unfolded."

But on the day we see him he is more eloquent and articulate than almost any political figure I have met. Remarkably for most people, politicians or otherwise, his speech is not punctuated with ums and errs. He speaks as if to be quoted or possibly in fear of being misquoted. His enunciation is clear, crisp and concise.

In February, when Tony Blair was asked in parliament by one of his own backbenchers to give a brief characterisation of the political philosophy which he espouses and which underlies his policies, he muttered something about the NHS and took his seat looking flummoxed. Ask Farrakhan what the Nation of Islam stands for and he does not miss a beat. "The core principles on which the NOI are found are one, freedom, two, justice and three, equality," he says. "All of this is inherent in Islam. We are Muslims. And we believe that we have been deprived of true freedom, true justice and true equality. So we petition the government of the US, since we live here, to give not only us that freedom, but give that freedom to all and justice to all and equity to all. And if we cannot get that within the political, economic and social environment within the United States then we ask to be separated into a state or territory of our own, where we would have a chance to give these rights which we have been denied, to ourselves."

So there it is. About as straightforward an enunciation of black nationalism as you can get from America's leading proponent of the cause. Almost 50 years after the US supreme court decision on Brown versus Board of Education outlawed segregation, the Nation of Islam points to the failure of integration and argues that when it comes to a judgment on "separate but equal", if they cannot have the equal, they would rather be separate. It is not a mainstream view, certainly. But in a country where voluntary segregation is both widespread and endemic it is hardly an extreme view either, particularly among African-Americans.

Even rightwing republicans express astonishment at his ban from Britain, which was repealed last July and then reimposed in April. Not because they like him, but because he has now become such a fixed point on the nation's racial landscape that even to most of his detractors he is no more than a familiar irritant. It has been generally, if begrudgingly, acknowledged that he represents something that needs to be taken account of, even if nobody is quite sure what that force is.

To that extent, both Farrakhan and the Na tion of Islam are as American as homecoming or the Superbowl. His message of self-help and strong community is deeply rooted in America's individualistic, pioneering psyche. "First we try to unite our people, pool our resources, build schools and economic development for ourselves and our people," he says. In a nation where organised religion plays a powerful force he is one among many. "We are trying to link with Muslims all over the world. We have got ten involved in politics because we recognise that there is a gain that we as a people can have if we get involved in politics - not as an ignorant person just throwing a vote away, but using our vote and leveraging our numbers and our money to see what we can extract from a recalcitrant system which has not given us what we feel our sacrifice, our suffering and the blood that we have shed has given us the right to have."

Born from a specific response to American racism during the 1930s and establishing itself primarily as a northern, urban force during the 50s and 60s, the Nation of Islam now has a strength in the US that it would be difficult to imagine a similar organisation possessing in any other country.

True there are sympathisers all over the world and followers in Canada, the United Kingdom and even Switzerland, but in nothing like the numbers and with nothing like the presence or influence that they have in America. That is why the ban on Farrakhan coming to Britain has been such a blow. The Nation sees Britain as the gateway to building a base among black, Arab and Asian youth around Europe and thereby gaining an international credibility that has thus far eluded it. Critics also believe that it gives the organisation a chance to revive its fortunes - both financially and politically.

"England is very, very important to the Nation of Islam for several reasons," says Vibert White, a former member of the Nation of Islam and professor at the University of Illinois. "It's a chance for Farrakhan to breathe new life into a movement which has really become stagnant in the last few years."

Farrakhan believes he has been denied access to a crucial audience. "What do I hope to accomplish on coming?" he asks. "To see those who follow me, to give the blacks, the whites, the Muslims, a chance to hear me and judge me for themselves."

Farrakhan believes it is his troubled relationship with the American Jewish community that forms the basis of his ban from the UK. He dates this back to his support for Jesse Jackson's presidential bid in 1984. African Americans and Jews form two of the Democratic party's most loyal constituencies. Farrakhan's supporters say that when it looked as though Jackson, by far the most pro-Palestinian contender, might win, the Jewish community got nervous and started to accuse him and his more controversial supporter, Farrakhan. "I think it's because after the Jesse Jackson campaign there was a polemic in dialogue between myself and the Jewish community," explains Farrakhan. "And because that dialogue was not resolved it meant the Jewish community in the UK utilised their influence to say that I was not a good person. So from that day to this I have been banned."

There is, of course, another version of events. After Jackson was lambasted for describing New York as "Hymietown" - for which he apologised - Farrakhan claimed that "Israeli hit squads" had been dispatched to kill him. He was briefly courted by the extreme right, who supported his calls for segregation and expressed hatred for Jews. In 1984, he said Israel will "Never have ... peace, because there can be no peace structured on injustice, lying and deceit and using the name of God to shield your dirty religion under his holy and righteous name." He had, in fact, accused others who he believed strayed from the tenets of their faith of following a dirty religion. "Sheikhs who live in opulence when their people live in squalor are practising a dirty religion," he said. "Christians [who] preach love, but practise hate and tyranny, use God to cover up their corrupt and dirty practices."

He did later apologise for using the phrase about Jews, saying it was "not appropriate" and "it was my mistake". But by now the die had been cast. Even those sympathetic to Farrakhan refer to him "flirting with the outrageous" and doing little to "dismiss the impression" of anti-semitism during the 80s. But most also agree that he has spent the past decade trying to patch these relations up.

He has had some success, notably his overtures to the Jewish vice-presidential candidate Joseph Lieberman during the 2000 election campaign fell on willing ears. But he expresses frustration that other attempts have met with constant rebuff.

"It cannot be resolved without dialogue. But it can be resolved," he says. "I've said to the Jewish community: 'If there's something that I said that is not truthful, then I do not want to be a party to that which is false, so if you can show me where what I said was error then you won't have to ask me to apologise, I will go before the World where I made the error and make the appropriate apology.' But that can't happen without a dialogue."

The fact that he remains a pariah to many, he believes, is due to the potency of the message passed down by the Nation of Islam's founder, the honourable Elijah Mohammed. "I believe that the message of truth from Elijah Mohammed is a threat to the control that many have had over black people and others as well," he says. "So they purposely put a veil over me that he is anti-white, anti-semitic, anti-American, he's anti-gay, he's anti-Christian. So when you put that on me, people of intelligence, rational people say: 'I don't want anything to do with that man.' That is exactly the intention of those in power. But we are gradually breaking those chains and coming out of this prison of media misrepresentation of Louis Farrakhan."

Farrakhan often talks about himself in the third person. Less lyrical in his speech than Jesse Jackson, his contemporary and regular confidant, he is also less evasive - giving answers to questions that are asked rather than set speeches he has pre-prepared. Nevertheless he is not short on rhetorical flourishes of his own, riffing on words or phrases until they become minor refrains. Style reinforcing substance to make the simple sound complex.

"First, raise the black man and woman from a state of economic, political, spiritual, mental, moral and social death," he says, when asked about the theme of his week-long trip to Los Angeles. "But then the whole of humanity is suffering. The whole of humanity is lost. So if that message of Islam can find us and reform us and make us better human beings, that same message is good for Latinos, that same message is good for Native Americans, that same message is good for the whites of America and the whole human family as well."

It is a far cry from the demagoguery you will see from him on stage. The short bursts of lectern-pounding rage that will intersperse his Castro-length, three- or four-hour long speeches. He once invited a select group of black journalists to his home in Chicago to ask them how he might handle his image better. They told him if he was worried about being misquoted he shouldn't speak for hours at a time. When Farrakhan tells an audience: "I'm gonna finish here," you know there is at least half an hour to go.

But while his tone and time-keeping may still vary greatly, the content of his speeches has, of late, become extraordinarily focused thanks to the events of September 11. After an initial vacillation, during which he went from condemning the attacks and US foreign policy to espousing outrageous conspiracy theories, he settled on a fairly consistent position against the war in Afghanistan. "I think the US government had every right to respond. But that response should have been appropriate to the wickedness perpetrated against the United States," he says.

The war, he believes, is driven by the desire for oil and could have been averted. "In the Holy Koran there is a scripture that says: 'Whenever an unrighteous person brings you news, you should look carefully into it less you should harm a people in ignorance rather than be sorry for what you did.'

"Afghanistan was never on the list of terrorist states, even though the Taliban were there and even though al-Qaida was there and even though Osama bin Laden was there. So Mullah Omar Mohammed asked President Bush: 'Show me this overwhelming evidence which you say you have and I will detain Osama bin Laden and turn him over to the relevant authorities.' And President Bush's response, which I don't think was proper, was: 'I'm not negotiating.' He said he showed this overwhelming evidence to Prime Minister Blair, but he was not going to bomb Prime Minister Blair and the United Kingdom, they were going to bomb Afghanistan, and so the Taliban deserved to know the truth and then see how they would react toward Osama bin Laden. Unfortunately they were not given that chance."

It is at this stage that one realises Farrakhan's unique position. He is America's most prominent Muslim. He also has no stake in the system as it stands. That makes him one of a handful of people in America who can draw a large crowd to denounce the war in almost any major city. There is no office he wishes to run for, no part of the white-dominated power structure with which he is in negotiation. In other words, he can say what he likes. For better, and sometimes for worse.

Halfway through the interview, a nurse comes in with some tablets. Farrakhan is still sick. His health is no personal matter. "Minister Farrakhan is the Nation of Islam," says Arthur J Magida, the author of Prophet of Rage: A Life of Louis Farrakhan and His Nation. "The nation relies on his charisma, his organisational skills and his image as perhaps the most courageous and defiant black man in the United States. If he is sick the Nation is sick."

This is not a problem unique to the Nation of Islam. Black America has long provided dynamic individuals, but they have rarely bequeathed vibrant or longstanding institutions. The Southern Christian Leadership Conference ceased to be a vital force when Martin Luther King died and the Rainbow coalition is little more than a platform for Jesse Jackson.

The internal structures of the Nation of Islam resemble a mixture of military and monarchy. No substantive decisions are made without him and yet for an organisation of the Nation's size to function decisions must be made in his absence. And so each layer of the organisation tries to anticipate what the stratum above wants, all the way up the pyramid. Initiative is discouraged; institutionalisation is embedded; individuality dissolves. Members move in swarms, following the most powerful in the pack. When two senior players meet, it looks like a scene from Goodfellas. The leaders shake hands and hug, then their entourages greet each other and for a moment they are all one. Then from this mingle of similarly dressed and identically coiffured humanity, they regroup into their two distinct entities, and head off in separate directions.

The end result is a mixture of officiousness and incompetence. Enduring constant, sour-faced, futile frisking in which one bag is checked twice and another not at all, waiting hours for Nation officials who claim they are only minutes away, watching men with earpieces strut purposefully around in circles, requiring identity tags that do not exist because they have not been issued: all creates the impression of an organisation in which people enjoy the trappings of authority but with neither the power to make it meaningful nor the system to make it workable.

Few would deny that the Nation of Islam and Farrakhan are problematic. His black nationalism and his history of inflammatory, anti-semitic remarks make both the message and the man unsavoury to some. But it is difficult to find anyone in America who seriously thinks his coming to Britain would be a problem either. The one thing that the Nation of Islam has never been associated with is violence towards other groups.

Violence within the organisation, following Malcolm X's departure in the 60s and Elijah Muhammad's death in the mid-70s, was intense. But there is scant evidence of violence towards Jews, whites or any other group.

"After all, Britain once ruled the entire world," argues Farrakhan. "Britain has nothing to fear from listening to a man and making their own judgment as to whether he is worthy of being listened to or discarded."

Since there is no reason to believe he would be a danger to public order, it is only his ideas that could pose a threat. And if Britain's multi-cultural society cannot challenge those head on, we can hardly blame Farrakhan for that.

·Correspondent, The Minister of Rage is on BBC2 on Sunday June 2 at 7.15pm.