Prepare for chaos. The latest work of art to adorn Trafalgar Square's Fourth Plinth will be a giant soapbox, which will give anyone who fancies it the chance to do whatever they want for an hour at a time.
After months of discussion, Antony Gormley's "haven for a certain degree of anarchy" became the latest joint winner of the Fourth Plinth project yesterday. The sculptor's One and Other soapbox project will go live next spring, although the costs of policing the platform – with "performers" replaced every hour, 24 hours a day – is as yet unknown.
"It's an opportunity to perform an act of collective creativity, people contributing one hour of their lives that represents Britain now," said Gormley, 57, adding that the exercise will present a national "portrait of this time".
Originally scheduled to run for 365 days, the Gormley project – which will incorporate a safety net around the plinth to prevent people falling off and will necessitate six curators to guard it day and night – has since been scaled back to 100 days. The hydraulic stairs he first proposed to transport people on to the plinth have also been replaced; now a crane will lift people up for maximum theatrical impact.
"I'm favouring a crane because it will be a moment of theatre, someone lifted from common ground and made into an image when they are on top of the plinth ... It will be a spectacle, but I'm also concerned about the subjects, what they learn about themselves, exposed in a public arena," he said.
Members of the public who wish to take part in the project will be able to apply online, with organisers saying they hope to avoid legal problems from impromptu speeches inciting racial hatred or violence by vetting applicants beforehand.
Gormley's artwork will be replaced by Nelson's Ship in a Bottle, a sculpture created by the second of yesterday's winners, Yinka Shonibare. The artist, born in London in 1962 but raised in Nigeria, has created a five-metre-scale replica of Nelson's ship, HMS Victory, in a giant glass bottle which will be lit up internally at night. Its sails are made from textiles bought from Brixton market in south London that reflect "the journey of the Empire".
Boris Johnson, the new Mayor of London who announced the winner yesterday, a day after his senior adviser, James McGrath, resigned after making offensive comments about Britain's black community, said he welcomed the multiculturalism of both artistic projects.
Shonibare said: "My win is extremely important. We all work in the interest of this nation, we pay taxes here. Multiculturalism is not divisive at all. It's about being one nation, being tolerant towards people who are different from us."
Mr Johnson said he continued to support the idea of a temporary statue of the RAF commander Sir Keith Park on the plinth in the run-up to the 70th anniversary of the Battle of Britain in 2010. He said he also supports a permanent statue of the former Air Chief Marshal elsewhere in the square.
But, Gormley said: "Trafalgar Square is a place of valedictory celebration of military heroes. We now live in a multicultural and less nationalistic time. The fact that Trafalgar Square is becoming a place of ethnic celebration, it seems necessary to register that change within the furniture of the square."
Gormley did have one new, and slightly unusual, suggestion: a statue of the Mayor himself. "The idea of Boris Johnson not saying anything but simply standing there, with his hair blowing in the wind, looking at the city which he has come to be Mayor of might be a very nice thing," he said.