Olympic theme at heart of Carnival this year

The west London event coincides with the closing ceremony of the Beijing Olympics on 24 August, when London officially takes up the mantle of Olympic city.

Mr Johnson said the carnival's theme will be Welcoming The World, reflecting the multicultural spirit of the event and the people across the globe who will visit London for the Games.

He unveiled the plans as he met carnival dancers and was treated to a series of performances that will feature at the festival.

But he stopped short of taking up an invitation to play the bongos, fearful of unflattering publicity shots.

Carnival organisers are working with the team behind the Games handover to erect a 25-square-metre screen in Emslie Horniman's Pleasance, a park near Ladbroke Grove, so crowds can watch the events in Beijing and London live.

The festival takes place over the bank holiday weekend with more than 1.5 million people expected to attend to enjoy the parade of artists from as far as Brazil and Nigeria. The Mayor said: "Notting Hill Carnival is an inimitable event, bringing people of all communities together from across the capital and beyond.

"It illustrates the energy and colour of our great city and this year's event, coinciding with the official handover ceremony at the Olympic Games, will be even more special. The world will be watching London as it accepts the flag and the challenge to stage the best Games ever in 2012.

"This will be a fantastic day out, as well as a historic moment."

Allyson Williams, interim chairwoman of London Notting Hill Carnival, said: "No other event in the UK comes close to matching the artistic spectacle of the carnival. We are proud to be working alongside London 2012, with both demonstrating the capital's ability to host world-class events."

The Mayor also highlighted his family connections to the carnival, having lived in Ladbroke Grove as a boy.

His spokeswoman said: "His aunts would come from all over the country to take part in the weekend-long festival so in fact he was dancing away to the festival years before William Hague or any of the Notting Hill Tory set."

The announcement came as police said they had started targeting potential knife thugs before this year's event. Officers are identifying criminals and troublemakers to keep them away from the festivities. Chief Inspector Jo Edwards said: "We'll be targeting those people we know are planning to go to Carnival simply to commit crime and making sure they can't."

He added that search operations would be put up at the entrances to the carnival to stop people taking in weapons.