Boris Johnson: I may become a romance writer

The Mayor joked that he will choose the name Rosie M Banks – the name of a recurring fictional character in books by P G Wodehouse.

Mr Johnson said: “In a trance, you will buy this blockbuster by Rosie M Banks and I hope to be somewhere quietly raking it in.”

Wodehouse’s Rosie M Banks is a romance novelist who his character Bertie Wooster describes as “the most pronounced and widely-read tripe on the market”.

Harry Potter author J K Rowling was last month unmasked as the writer of detective novel The Cuckoo’s Call by Robert Galbraith.

The Mayor also used his trip to Australia to give his strongest endorsement of Mr Cameron yet, saying that he will be the Prime Minister for a “very long time”.

Asked during a radio interview about his own leadership ambitions Mr Johnson said: “[David Cameron has] got to get on and be Prime Minister and he will go on and be that for, I think, a very long time.”

Mr Johnson added: “If you look at what’s happening I Britain, the offering from the Labour Party is pitifully thin. It’s not at all clear what Ed Miliband and his guys stand for and I think David Cameron’s set there for a long spell."

Mr Johnson is regarded by many Tories as the strongest contender to replace Mr Cameron.

However, some suspect the mayor of talking up a Tory election victory in order to increase the chances of the party removing Mr Cameron in the event of a hung parliament in 2015.