London Mayor upstages PM Cameron at party conference BIRMINGHAM, England (Reuters) - Maverick London mayor Boris Johnson, one of the most colorful figures in British politics, received a hero's welcome at the ruling Conservative Party's conference on Monday, underlining his status as a possible future challenger to struggling Prime Minister David Cameron. Activists cheered Johnson as he arrived by train for the conference in the industrial city of Birmingham. Hundreds later packed a conference fringe meeting addressed by the mayor, whose feverish atmosphere had the air of a campaign rally. Johnson, who won re-election last May against the national trend, used the occasion to give Prime Minister David Cameron pointed advice on how to win the next general election in 2015 while pledging loyalty to the British leader. "It is sometimes inevitable that the mayor of a great city will find himself say things that seem to be at variance or ahead of national policy," Johnson said with a smile. Sporting a mop of fair hair and a robust, humorous speaking style that electrifies many voters, Johnson delights in the limelight that speculation about his political future has provoked. He denies any designs on the top job. "No one as a result of that should have any cause for doubt about my admiration for David Cameron," he insisted, saying he had backed Cameron's bid for the party leadership in 2005, long before many colleagues. But while support for Cameron's government has slid amid recession and spending cuts, Johnson's popularity has soared on the back of a successful Olympic Games that saw Team GB win a record haul of medals. Using his May victory in mayoral elections against Labour's Ken Livingstone as an example, Johnson said the Conservatives needed to get their message out to voters to prevent Labour leader Ed Miliband and shadow finance minister Ed Balls winning power in 2015. "We did it against the odds and we stopped our capital from falling once again into the hands of a cabal of semi-reformed Marxists," Johnson told activists at the Conservative Party conference in the English city of Birmingham. "If we can get the message out over the next two years about what the government is doing and why it is doing we can save this country from the return of the two Eds as we saved London from Livingston in 2012," he said to a standing ovation. Arriving by train to a scrum of reporters and chants of "Boris, Boris" from fellow passengers, Boris was treated to a standing ovation when he addressed a conference room with hundreds of cheering supporters. Peppering his speech with everything from anecdotes about squirrel attack to jokes about Arnold Schwarzenegger, Johnson pledged to give free London tube transport to serving members of the armed forces in uniform, drawing cheers. One Conservative group even produced a special newspaper devoted to Johnson listing ministers who would serve in "Prime Minister" Boris's dream cabinet. That is an unwelcome irritant for Cameron as he struggles with a recession, a coalition government that is divided over Britain's relationship with the European Union and party grumbling that its leader fails to enthuse aspirational voters. "David Cameron may not stir Tory hearts and he may not have delivered an election victory but he's far from down and out," Tim Montgomerie, editor of the ConservativeHome Website, wrote in the special newspaper devoted to Boris. A poll of 1,872 Conservative members showed that two thirds believed Labour would win the next election and that only a third thought the Conservatives would win. It showed 37 percent would like Johnson to succeed Cameron if he lost the next election. But Johnson's future is shackled by the lack of a seat in parliament and a perception that he is too quirky and eccentric for the top job. "My advice to him would be that it is the kiss of death to most political careers to be named as the next prime minister years before there is likely to be a vacancy," Kenneth Clarke, a minister in Cameron's government, told Reuters. God knows who would be contenders for prime minister when the post eventually becomes vacant. It is all complete nonsense - there is no prime ministerial contest going on. It is pure conference nonsense," Clarke said. Editing by Michael Stott