The men who would be mayor

Five hundred architects, developers and politically engaged punters filed into the Queen Elizabeth Hall on London's South Bank last Thursday evening in search of ideologically charged debate from the capital's leading candidates.

The two big hitters had swapped their traditional sides for the occasion. On the far left of the stage sat the Conservative Steven Norris, all City slick and alpha male, whereas at the extreme left, hunched in a crumpled suit and sporting a grumpy visage, was Labour's prodigal son, Ken Livingstone. Between them were Simon Hughes, the Liberal Democrats candidate, and Darren Johnson of the Green Party, and at the helm sat Architecture Foundation head Rowan Moore.

Whether or not you like Heron Tower, these are my decisions. If you don’t like me, vote me out

Ken Livingstone, Labour

As it turned out, the terrain was less dangerous than one might have thought. The candidates appeared to be in broad agreement on many of the key issues. All of them accepted the need for more sustainable housing, were supportive of the controlled development of tall buildings and were happy with a hefty chunk of affordable housing.

The consensus stretched across political lines: the Greens' Darren Johnson didn't mind skyscrapers if they were clustered; Tory Steven Norris spoke solemnly about possible tax breaks on sustainable materials and even supported 50% affordable housing (albeit "dependent on the site"). What was going on?

First off, all four candidates were asked to present their "Vision for London", which they tackled with varying degrees of success. Lib Dem Simon Hughes went first, explaining in his excited headmasterish manner that design should be "principally aimed at the masses, not the classes". Darren Johnson followed, unveiling his secret weapon for the capital: 1000 new allotments. Livingstone was next, washing away the arguments of the previous two with a flood of statistics. Norris bought up the rear with the intriguing suggestion that some of the 800,000 extra inhabitants anticipated in London by 2016 could instead be accommodated in the North-east of England – a sentiment echoed by Hughes.

The government has been useless in moving forward Crossrail

Simon Hughes, Liberal Democrats

The main debate about architectural quality was cursory, to say the least. Livingstone didn't like the initial designs for the Barking Reach community in the Thames Gateway comprising only 6,000 homes (density has now been revised to 12,000-20,000 homes); Norris was repelled by Richard Rogers' Lloyds Building ("It's got all the plumbing on the outside," he complained); Hughes was unimpressed by the designs for the Potters Field development next to Tower Bridge ("Those cylindrical things are ghastly"); and Johnson, predictably, loved BedZED.

The real arguments were over the extent of mayoral powers. Both Norris and Hughes thought the mayor should leave the 33 London authorities to get on with it over issues of planning. Livingstone was considerably more blunt, and flared up when it was suggested his exclusive power to reject major planning applications was undemocratic. "Whether or not you like the Heron Tower or the London Bridge Tower, these are my decisions," he said. "If you don't like me, vote me out."

All except Livingstone agreed that major decisions, such as planning consent for Renzo Piano's London Bridge Tower, Europe's tallest building, should be presided over by a Greater London Authority panel rather than being left down to one man. Here, Livingstone seized the opportunity to have a pop at "those awful people from English Heritage", who "having got jobs themselves couldn't give a sod whether anyone else gets one."

It was the same story over Livingstone's Architecture and Urbanism Unit. Chaired by Richard Rogers, the unit holds an influential role in advising the incumbent mayor on design quality. Norris and Hughes, however, recoiled from the idea that the mayor was "the sole arbiter of architectural taste in London". Like a good business executive, Norris pledged to halve the unit's size, whereas Hughes promised to scrap it and fire Rogers in favour of a new panel of the "next generation of young architects". Hughes also wanted all areas of London to be championed and not just the glamorous ones: "I want people to get enthusiastic about Hillingdon!" he said, rather unconvincingly.

The only major flashpoint came when Hughes repeated his claim that it was a disgrace that Livingstone allegedly had not been to see Gordon Brown in his four years in charge. In particular, Hughes accused Livingstone of failing to lobby the government for funding for the infamously uncertain Crossrail project. This forced the mayor onto the offensive: "That's just complete bollocks," he said bluntly. Livingstone went on to elaborate, claiming to have had off-the-record assurances from "the three most senior ministers in government" that Crossrail would happen.