Boris in bid to become London mayor

The colourful Conservative MP for Henley held a photo call at City Hall to promote his nomination, but was mobbed by the media and escaped on his bike. "It's a riot," he said before pedalling away, watched by puzzled tourists.

Fighting through the scrum Mr Johnson managed to say: "I think it is amazing that people do not want to do this job. It is an amazing city. I'm thrilled and excited, but we are at a very early stage."

He resigned as higher education spokesman in Conservative leader David Cameron's front bench team on Monday to concentrate on the race for mayor but will remain as a constituency MP. His announcement, after weeks of agonising, came just hours before the noon deadline for applications for the Conservative nomination to stand against Labour's Ken Livingstone in next year's election.

More than 40 would-be candidates have submitted their names and a committee will now whittle them down to a shortlist to go forward to an open primary election, with voting in September.

Mr Johnson is expected to be unveiled at its annual autumn conference in Blackpool.

Earlier Mr Johnson said: "London is an outstandingly varied and beautiful place and it deserves a proper debate. I want to bring fresh ideas to the capital and offer a new direction for Londoners. I believe that the Mayor of London should keep things simple and direct his or her intellectual energy at the core problems that affect people's everyday lives.

"Even the greatest cities have further greatness in them. I will stand for a greater London and for putting the smile back on London's face."

He said he plans to announce detailed proposals later in the summer.

The Tories had been struggling to find a high-profile candidate to take on Mr Livingstone, who is seeking his third term. Greg Dyke, Sir John Major and Sir Digby Jones were not persuaded to stand. They were forced to delay the deadline for applications amid reports that no candidates of sufficient prominence had put themselves forward. Although he has a reputation for gaffes and a complicated personal life, Mr Johnson is one of the Conservative's most popular and best-known faces, thanks partly to appearances on TV shows such as Have I Got News For You.