English Defence League leader Tommy Robinson has been arrested on a controversial march that was prevented from going through the centre of one of Britain's biggest Muslim communities.
A tweet on the EDL website stated: "Tommy's been arrested for incitement."
A Metropolitan Police spokesman said: "A 30-year-old man was arrested for breaching section 14 of the Public Order Act 1986 and inciting others to breach section 14 of the Public Order Act 1986.
"He has been taken to a central London police station where he currently remains."
The far-right EDL had lost a High Court battle over where its members are allowed to demonstrate.
The organisation had wanted to hold the rally in an area in Tower Hamlets, east London, which it says is "subject to Sharia law".
But judge Mr Justice King ruled that a police decision to impose restrictions over fears of serious public disorder was reasonable and proportionate.
By 6pm on Saturday, 14 people had been arrested, but it is thought the numbers may have risen.
The Met Police allowed the protest to go ahead, but under strict conditions which meant any march would be held at the outskirts of the borough and close to Tower Bridge.
A counter demonstration was held by anti-fascist and anti-racist groups. Their supporters were among those arrested.
Offences ranged from possession of a pointed blade, possession of a firework, breach of public order, criminal damage and violent disorder.
They are all being held at police stations in east and central London.
Among those in custody is a 15-year-old boy who was arrested for going equipped, Scotland Yard said.
He has been taken to an east London police station where he currently remains.