At his first official engagement - a visit to a cultural event in Trafalgar Square marking the Sikh new year festival of Vaisakhi - Mr Johnson pledged to work for all communities and to unite the city in his new role.

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 capital's first Tory mayor will begin a series of interviews to pick the team that will advise him in the post.

Mr Johnson said he had demanded tough action on crime in the city during his 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.

"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."