Members of the EDL waved flags and chanted football songs
Controversial Dutch MP Geert Wilders has shown his anti-Islam film in the UK's House of Lords, sparking angry scenes outside Parliament.
About 200 members of the English Defence League marched in support of Mr Wilders as police tried to keep apart anti-fascist counter-protesters.
The Met Police said 50 people, mostly counter-protesters, were arrested.
Freedom Party leader Mr Wilders, previously banned from the UK, says Islam and democracy are "incompatible".
The politician attempted to enter Britain last February, but was ordered to fly back to the Netherlands hours later. In October, the ban was overturned.
'Welcome to stay'
Mr Wilders said the film and subsequent discussion was attended by about 60 people.
At a press conference afterwards, he called for an end to immigration to Europe from Islamic countries, but said Muslims who agreed to obey the law of the land would be welcome to stay.
Dutch politician Geert Wilders is leader of the Freedom Party
Several hundred members of the English Defence League (EDL) marched past the Houses of Parliament in support of the Dutch politician.
Flanked by mounted police, they chanted football songs and waved Cross of St George flags.
They were kept apart from dozens of anti-fascist demonstrators, who gathered outside the Houses of Parliament, by police officers.
The Unite Against Fascism organisation protested against the visit of Mr Wilders and the EDL march.
The Dutch politician is a guest of cross-bencher Baroness Cox and UK Independence Party leader Lord Pearson.
Lady Cox said the visit had been a victory for free speech, saying: "You don't have to agree but it is important to debate sensibly in a responsible and very democratic way."
The Home Office said it is opposed to "extremism in all its forms".
A spokesman said the government "regrets the decision by Baroness Cox and Lord Pearson to invite Geert Wilders to the House of Lords for a private showing of his film Fitna".
"However, we currently have no reason to deny Mr Wilders admission to the UK," he added.
The Freedom Party recently made major gains in local elections in the Netherlands, becoming the biggest party in the medium-sized city of Almere and the second largest in The Hague, which is the country's political capital.
The Dutch MP has called the Koran a "fascist book".
His film caused outrage across the Muslim world when it was posted on the internet in 2008.
Fitna's opening scenes show a copy of the Koran followed by footage of the 9/11 attacks in the US and the bombings in Madrid in 2004 and London in 2005.
Mr Wilders has had 24-hour protection for the past five years after receiving death threats for his views.
The Dutch politician had been due to show his film at the House of Lords last year when the then Home Secretary Jacqui Smith said his presence had the potential to "threaten community harmony and therefore public safety", prompting the ban on him entering the country.