London police said on Wednesday they would mount an "unprecedented" operation this weekend to prevent violence and serious disorder when two large protests - anti-immigration and pro-Palestinian - take place in the British capital.

At least 80,000 people are expected in London on Saturday for the two demonstrations - a pro-Palestinian march marking Nakba Day and another 'Unite the Kingdom' rally organised by the anti-Islam activist Stephen Yaxley-Lennon, better known by his pseudonym Tommy Robinson.

With the football FA Cup final also being staged at Wembley in the northwest of the capital, and against a backdrop of global tensions, recent antisemitic attacks, and a raising of Britain's terrorism threat level, police said they would be using "the most assertive possible use of our powers" to forestall trouble.

"The scale of the operation is unprecedented in recent years," Deputy Assistant Commissioner James Harman told reporters, saying it would involve some 4000 officers backed up by helicopters and dog…