Boris pledges to unite Londoners

Mr Johnson had his first official engagement with a visit to a noisy cultural event in Trafalgar Square marking the Sikh festival of Vaisakhi.

He dismissed the suggestion made during the election campaign that he would not support events such as this as "a canard floated by the outgoing Mayor".

The Mayor-elect, who seized City Hall from Labour's two-term incumbent Ken Livingstone, said he had demanded tough action on crime in the city during a meeting with Metropolitan Police Commissioner Sir Ian Blair.

"I made it very clear that I want to see a dramatic reduction in crime, beginning with driving out so-called minor crime, particularly in the areas for which the Mayor has responsibility, and above all on public transport," he said.

Dozens of well-wishers thronged to meet Mr Johnson as he toured the stalls, congratulating him and posing for photographs.

Mr Johnson seemed delighted with the reception, greeting people warmly and even posing for photographs in a policeman's cap.

"The last few days have been very, very exciting and very, very exhausting, but this is the single most wonderful job in British politics," he said. "It's a fantastic chance to give a voice to London and unite London. I am going to be a Mayor for all London and work to unite communities. One of the wonderful things we have got in London is fantastic diversity - we have got the whole world in a city."

Reiterating the words he said when he signed the declaration of acceptance, Mr Johnson said that violence among young people was the single biggest problem facing the city.

Mr Johnson said he hoped there would be a boom in the provision of educational and social activities to keep children off the streets and cut the problem of teenage violence.