"A Muslim man with way too many extremist links to be entirely coincidental is now the Mayor of London. I suppose this is hardly a shock, though. The native English are a demographic minority (and a rapidly dwindling one) in London, whilst Muslims from Pakistan and Bangladesh are a rapidly expanding demographic." — British politician Paul Weston.

"I regret giving the impression I subscribed to their views and I've been quite clear I find their views abhorrent." — Sadiq Khan.

In 2008, Khan gave a speech at the Global Peace and Unity Conference, an event organized by the Islam Channel, which has been censured repeatedly by British media regulators for extremism. Members of the audience were filmed flying the black flag of jihad while Khan was speaking.

"The questions are genuine, they are serious. They are about his willingness to share platforms with people who want to 'drown every Israeli Jew in the sea.' It's about his having employed someone who believed the Lee Rigby murder was fabricated. It's about his career before being an MP, coaching people in how to sue the police." — Conservative Party candidate Zac Goldsmith.

Conservative Party candidate Zac Goldsmith accused Khan of giving "platform, oxygen and cover" to Islamic extremists. He also accused Khan of "hiding behind Britain's Muslims" by branding as "Islamophobes" those who shed light on his past.

Labour Party politician Sadiq Khan has been sworn in as mayor of London. He is the first Muslim to lead a major European capital.

Khan, 45, is the London-born son of Pakistani immigrants. His father was a bus driver and he grew up with seven siblings in a government-subsidized apartment. He studied law, became a university professor and served as chairman of the civil liberties pressure group Liberty. He was elected to Parliament in 2005. Khan's supporters say he is the epitome the Muslim immigrant success story.

Khan — who won 57% of the ballot, or 1.3 million votes, a number which happens to be roughly equal to Muslim population of London — has promised to be "the British Muslim who takes the fight to the extremists." Others are not so sure. During the election campaign, Khan faced a steady stream of allegations about his past dealings with Muslim extremists and anti-Semites.

Khan's opponent, Conservative Party politician Zac Goldsmith, drew attention to Khan's past career as a human rights lawyer that included repeated public appearances alongside radical Muslims.

Goldsmith accused Khan of giving "platform, oxygen and cover" to Islamic extremists. He also accused Khan of "hiding behind Britain's Muslims" by branding as "Islamophobes" those who shed light on his past.

In an interview with the London Evening Standard, Goldsmith said:

"To be clear, I have never suggested he [Khan] is an extremist but without a shadow of doubt he has given platform, oxygen and cover to people who are extremists. "I think he is playing with fire. The questions are genuine, they are serious. They are about his willingness to share platforms with people who want to 'drown every Israeli Jew in the sea.' "It's about his having employed someone who believed the Lee Rigby murder was fabricated. It's about his career before being an MP, coaching people in how to sue the police. "It just goes on and on and on. To pretend those are not legitimate questions, to pretend that by asking those questions newspapers, Londoners or my campaign are engaging in Islamophobia is unbelievably irresponsible. "It is just obscene that somebody who wants to be the mayor of the world's greatest city, to be in charge of our police and security, should behave not only with such bad judgment but in a way that is totally shameless."

Goldsmith also drew attention to Khan's ties with Suliman Gani, a Muslim cleric in Tooting, the constituency in South London where Khan is an MP. "To share a platform nine times with Suliman Gani, one of the most repellent figures in this country, you don't do it by accident," Goldsmith said.

Goldsmith was referring to a Sunday Times exposé, which revealed that between 2004 and 2013, Khan had spoken alongside Gani on at least nine occasions, "even though Gani has called women 'subservient' to men and condemned homosexuality, gay marriage, and even organ transplants."

Gani — who has ties to the extremist Islamist group Hizb-ut-Tahrir, and has rallied in support of Shaker Aamer, an al-Qaeda terrorist who was detained at Guantanamo Bay — is also linked to the London-based Tayyibun Institute, which the British government says "tolerates or promotes non-violent extremism."

According to the Times, on the night of the Paris attacks in November 2015, Gani appeared at an "Islamic question time" event in Bedford, where speakers reportedly told British Muslims to "struggle" for an "Islamic state."

Khan and Gani first shared a platform in August 2004 at an event organized by Stop Political Terror, a group supported by Anwar al-Awlaki, a radical American imam who was killed in 2011 by a CIA-led drone strike in Yemen. According to the Times, Khan spoke at least four times at events organized by Stop Political Terror, which has since merged with CAGE, a group that called the Islamic State butcher Jihadi John a "beautiful young man."

In an interview with the Times, Davis Lewin, deputy director of the Henry Jackson Society, an anti-extremism think tank, said:

"Gani has campaigned on behalf of convicted terrorists, appeared at events designed to undermine government counter-radicalization strategies, including sharing platforms with a pro-terrorist organization such as CAGE, and is said to hold repugnant views about women and the lesbian, gay, bisexual, trans community. "Given that the UK, and London in particular, is a major target for Islamist-inspired terrorist attacks, it is intolerable to see any politician, much less one seeking such a vitally important office as mayor of London, associate with an individual such as this. "Mr Khan's reportedly repeatedly sharing a platform with this man, whose views are widely available, is deeply alarming."

Khan also spent years campaigning to prevent Babar Ahmad from being extradited to the United States on charges of providing material support to terrorism. Ahmad, who admitted his guilt, later said that his support for the Taliban was "naïve."

In 2002, Khan represented the leader of the Nation of Islam, Louis Farrakhan. Khan tried to reverse a decision by the Home Office, which had banned Farrakhan from entering the UK due to fears that his anti-Semitic views would stir up racial hatred. Farrakhan has called Jews "bloodsuckers" and referred to Judaism as "a gutter religion."

At the time, Khan said: "Mr. Farrakhan is not anti-Semitic and does not preach a message of racial hatred and antagonism." Khan added:

"Farrakhan is preaching a message of self-discipline, self-reliance, atonement and responsibility. He's trying to address the issues and problems we have in the UK, black on black crime and problems in the black community. It's outrageous and astonishing that the British Government is trying to exclude this man."

Khan now says: "Even the worst people deserve a legal defense."

In 2004, Khan was the chief legal advisor to the Muslim Council of Britain, a group linked to the Muslim Brotherhood. Khan defended Yusuf al-Qaradawi, an Egyptian-born Islamist who has been banned from entering the UK. Al-Qaradawi has expressed support for Hamas suicide bombings against Israel: "It's not suicide, it is martyrdom in the name of Allah." According to Khan, however, "Quotes attributed to this man may or may not be true."

Also in 2004, Khan shared a platform with a half-dozen Islamic extremists in London at a political meeting where women were told to use a separate entrance. One of the speakers was Azzam Tamimi, who has said he wants Israel destroyed and replaced with an Islamic state. Another speaker was Daud Abdullah, who has led boycotts of Holocaust Memorial Day. Yet another speaker was Ibrahim Hewitt, a Muslim hardliner who believes that adulterers should be "stoned to death."

In 2006, Khan attended a mass rally in Trafalgar Square to protest the publication of cartoons of Mohammed by Western newspapers. One of those present at the rally was Tamimi, who told Sky News: "The publication of these cartoons will cause the world to tremble. Fire will be throughout the world if they don't stop." Khan defended Tamimi: "Speakers can get carried away but they are just flowery words."

In 2008, Khan gave a speech at the Global Peace and Unity Conference, an event organized by the Islam Channel, which has been censured repeatedly by British media regulators for extremism. Members of the audience were filmed flying the black flag of jihad while Khan was speaking.

Also in 2008, Khan wrote that Turkey should be allowed to join the European Union in order to prove that the bloc is not a "Christian Club" that discriminates against Muslims:

"Muslims across Europe will see the question for Turkish admission to the EU as a clear test of European inclusion. If the door is slammed shut it will be understood by 20 million Muslim citizens of the EU that the basis of the decision to treat Turkey differently to new members like Bulgaria or Romania has been made on the basis that Europe is a 'Christian Club.' "Some will see this as a clear indication that Muslims can never be a part of the story of Europe or the West. That will undermine everybody working to say that of course one can be British, European and Muslim, or French, European and Muslim."

In 2009, when Khan was the Minister for Community Cohesion in charge of government efforts to eradicate extremism, he gave an interview to the Iran-backed Press TV. He described moderate Muslims as "Uncle Toms," a racial slur used against blacks to imply that they are too eager to please whites.

In the same interview, Khan expressed support for boycotts of Israeli products: "You know, there's nothing wrong, and I encourage people to protest, to demonstrate, to complain, to write into newspapers and TV, to, if you want to boycott certain goods, boycott certain goods — all lawful means open in a democratic society."

In 2012, Khan addressed and praised the Federation of Student Islamic Societies (FOSIS), an umbrella group founded by activists from the Muslim Brotherhood. The British government has criticized FOSIS for promoting Islamic extremism.

In 2014, Khan expressed support for Baroness Warsi, who resigned from Prime Minister David Cameron's cabinet because she felt that Cameron was insufficiently critical of Israel. In an essay for the Guardian, (which has now been removed from the Guardian's website) Khan wrote:

"Warsi must be listened to when she says, 'our response to [Gaza] is becoming a basis for radicalization that could have consequences for us for years to come' [...] The government's failure to criticise Israel's incursion is not just a moral failure — it goes directly against Britain's interests in the world and risks making our citizens less safe as a result."

Commentator Anthony Posner wrote:

"Although Khan has assured Londoners that he would not use the mayoral office as 'a pulpit to pronounce on foreign affairs,' one wonders if he would really be able to remain neutral if London was once again dealing with large anti-Israel demos. On the basis of his response to Warsi's resignation, it seems unlikely that he would show restraint."

In March 2016, Khan was pressured to fire a top aide, Shueb Salar, after the Daily Mail revealed that Salar was sending misogynistic messages on social media: "Along with homophobic and sexist comments, Salar jokes about rape and murder, claims Bengali people 'smell' and said he thought the slaying of soldier Lee Rigby by extremists in 2013 may have been fabricated."

In May, a close ally of Khan, Labour politician Muhammed Butt, apologized for sharing a Facebook post which compared Israel with Islamic State.

In an election debate aired by the BBC on April 18, Khan said he had "never hidden" the fact that he had represented "some pretty unsavory characters." When asked if he regretted sharing a platform with extremists, he said: "I regret giving the impression I subscribed to their views and I've been quite clear I find their views abhorrent."

Former Labour Party manager Rob Marchant said he was worried about Khan's links to extremists, but that he should be given the benefit of the doubt:

"While this dabbling with Islamist politics may well have been more to do with a streak of ruthless populism in Khan in building political support, than a genuine meeting of minds with the Islamists, it does cast some doubt upon both his judgement and his values."

By contrast, British politician Paul Weston, who has long cautioned about the Islamization of Britain, warned that Khan's rise is a harbinger of things to come:

"The previously unthinkable has become the present reality. A Muslim man with way too many extremist links to be entirely coincidental is now the Mayor of London. I suppose this is hardly a shock, though. The native English are a demographic minority (and a rapidly dwindling one) in London, whilst Muslims from Pakistan and Bangladesh are a rapidly expanding demographic..... "In a couple more decades Britain may well have its first Muslim Prime Minister, and I think we can safely assume he will be of the same ideological stock as Sadiq Khan.... Reality cannot argue with demographics, so the realistic future for Britain is Islamic."

Soeren Kern is a Senior Fellow at the New York-based Gatestone Institute. He is also Senior Fellow for European Politics at the Madrid-based Grupo de Estudios Estratégicos / Strategic Studies Group. Follow him on Facebook and on Twitter. His first book, Global Fire, will be out in 2016.