Tens of thousands of protesters marched through central London on Saturday, carrying flags of England and Britain, for a demonstration organised by the anti-immigrant and anti-Islam activist Tommy Robinson.

Police said they would have a huge presence in the British capital. A "Stand Up to Racism" counter protest was also due to meet nearby, following a highly charged summer in Britain that has seen protests over immigration and free speech.

By midday tens of thousands of protesters were packed into streets south of the River Thames, before heading towards Westminster, seat of the UK parliament.

Demonstrators carried the Union flag of Britain and the red and white St George's Cross of England, while others brought American and Israeli flags and wore the MAGA hats of US President Donald Trump. They chanted slogans critical of Prime Minister Keir Starmer and carried placards including some saying "send them home". Some attendees brought children.

Robinson has billed the Unite the Kingdom march as a celebration of free speech. It is also expected to mourn Charlie Kirk, the American conservative activist shot dead on Wednesday. "Hundreds of thousands already pack the streets of central London as we Unite as one for our freedoms," Robinson said on X.

Britain's biggest anti-immigrant political party, Reform UK, which has topped opinion polls in recent months, has kept its distance from Robinson, who has several criminal convictions.

London's Metropolitan Police has said it would have more than 1,600 officers deployed across London on Saturday, including 500 brought in from other forces. In addition to policing the two demonstrations, the force was stretched by high-profile football matches and concerts.

"We will approach them as we do any other protests, policing without fear or favour, ensuring people can exercise their lawful rights but being robust in dealing with incidents or offences should they occur," said Commander Clair Haynes, who was leading the policing operation. (Reuters)