London's mayoral contest features seasoned operators vying to govern the world's top financial centre in the closest thing Britain has to the drama of a U.S. presidential election.

The introduction of driverless underground trains against trade union resistance has become a highly symbolic issue for Johnson as he strives to show an assertive side.

The tousle-headed Conservative coats his upper-class manner with a veneer of bumbling that has shielded him from some of the acrimony directed of late at Prime Minister David Cameron over a privileged background that sits uncomfortably in a time of austerity.

"If you have directly elected mayors you go for celebrity not political party skills, and Boris is a celebrity," said George Jones, Professor of Government at the London School of Economics.

"Boris is no fool, he likes to play the joke - it means he can get away with all sorts because he's funny," Jones said.

But not everyone is convinced by the witty persona projected in television quiz shows and jokey asides. Behind the sunny image, some see a 'reactionary Tory' of the old school.

Johnson's chief rival Ken Livingstone, a firebrand leftist during prime minister Margaret Thatcher's crackdown on unions in the 1980s, accuses him of making a mess of one of the world's oldest underground railways.

Fares have risen and delays or line shutdowns for weekly 'upgrades' are the bane of Londoners' lives.

Johnson's proposal to replace drivers on the underground, or "The Tube", with automated trains and lesser paid "train captains" has raised howls from London's powerful rail unions - one of the few syndicates who can still bring the capital to a standstill, even in the year when London hosts the Olympic Games.

"You've got to take the decisions in the next four years, when you're buying the new trains, that we never again have an old fashioned cab with a driver in it that we've got at the moment," Johnson told Reuters at a campaign event last month.

The manning of trains has a particular resonance in the history of British trade union conflict. Unions defended the double manning of locomotives, on safety grounds, years after the 1968 withdrawal of mainline steam trains meant firemen were no longer needed to stoke the coals.

In parts of Europe, the concept of the "stoker in the electric locomotive" became something of a byword for the 'English disease' of industrial conflict in 1970s Britain.

The debate over train manning comes amid trade union concern over public sector cuts and stagnation in the private sector.

"There will be unions taking a more active role in many workplaces because of the downturn, because issues such as pay and redundancy have really come to the fore," a Trades Union Congress spokesman said.

While strike action is much rarer than in the 1970s, last year's public sector strikes caused a dramatic spike in days lost over the 12 months to January 2012. Over 1.4 million days were lost, almost four times more than in 2010.

The November 2011 strike was dubbed "the biggest in a generation". It caused the largest monthly number of days lost to strikes since the July 1989 national dockers strike.

Tube drivers, who earn almost twice the average British wage, are the latest unionised workers in the spotlight over costs.

Johnson says the running costs of the tube versus the Docklands Light Railway, which is driverless and uses train stewards, make clear the case for automation.

"What it will do is it will stop old-fashioned trade union leadership using old-fashioned practices to restrict progress," he said. "There could be some union barons...who could object to this approach. And if in the course of that argument their influence is diminished that would be no bad thing."

THE UNION MAN

Bob Crow, the general secretary of the National Union of Rail, Maritime and Transport Workers, thinks Johnson's plan an electoral gimmick. Unions could not allow it, on safety grounds.

Crow speaks with a brusque East London accent, a stark contrast to Johnson. He frames business as a class struggle between employees and bosses.

A powerful voice in London, he is determined to protect the rights and benefits of his workers at any cost.

"We'll strike any time. It's irrelevant whether the Olympics are on or not. We're not being blackmailed by saying that because the Olympics is on, then we can't doing anything about it," Crow told Reuters.

"(Johnson) keeps on saying that they've got driverless trains on the Docklands Railway. Well, Docklands Railway is purposely built - it's above ground except for one station - and it's built on the basis that if anything happens, emergency services can get there as soon as possible."

The vulnerability of the tube system was demonstrated when militant Islamists detonated suicide bombs in tunnels in 2005. On a more banal level, commuters are familiar with the unpleasant minutes when trains halt in tunnels between stations.

Crow said he could not see how a train captain could function effectively on tube trains routinely packed at rush hours.

"What would the train captain do? Because the trains are so packed he won't be able to move around the carriages because they will be stacked with people," Crow said.

The enmity between the Johnson and Crow is well-established from Johnson's first term as mayor, where the pair faced off over closing tube ticket offices, generous Olympic bonuses for workers, and rows over rotas, some of which led to strikes.

Crow has been directly featured in Johnson's campaign literature casting him as a union bogeyman. He is suing Johnson for what he alleges is Johnson's attempt to wrongfully link him to rival candidate Livingstone.

"It's unusual to have your name up on a poster in an election campaign linking you to someone you're not supporting," he said.

THATCHERITE ECHOES

After months of running level, the latest data from a March 20 Ipsos MORI poll show Johnson eight points ahead of former Labour mayor Livingstone, who ran the city from 2000 to 2008.

One explanation for Boris's appeal has been that he is seen as being willing to take on the unions in a battle reminiscent of the 1980s when unions were powerful national forces.

"There are not many powerful unions left in Britain. But rail unions, particularly in London, still have significant power and are willing to wield it," said Professor Philip Cowley of the University of Nottingham.

Rail disruption is something that has a particularly galvanizing effect on public opinion. No one wants to be delayed going to work or getting home. In this sense, Johnson might feel himself to be picking a fight with a vulnerable opponent.

Britain has a history of government showdowns with powerful unions, one of the most dramatic being a year long strike by British miners in 1984 when Thatcher took on the powerful National Union of Mineworkers, led by Arthur Scargill, and won.

"In this particular respect (Johnson) is facing what Mrs. Thatcher faced with Scargill," politics expert Jones said.

Johnson himself would not respond directly to whether he considered himself a "Thatcherite" in taking on train drivers' unions. So was being a Thatcherite a bad thing?

"No. Well you know, I'm in favour of progress," he said.

(Reporting By Ethan Bilby, editing by Ralph Boulton)

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