LONDON — It's art for the people, of the people — and definitely by the people.

A 35-year-old mother of two stepped onto a 23-foot-high stone plinth in Trafalgar Square on Monday, kicking off an ambitious art project that puts members of the British public on display in the iconic plaza alongside statues of 19th-century military heroes.

Artist Antony Gormley, who came up with the idea, said it provides "a living picture" of Britain "in all its wonderful difference."

The 2,400 participants, chosen at random from thousands of applicants, include an Elvis impersonator, a man on a folding pink bicycle and a woman dressed as a pigeon. Each will spend an hour on the 5- by 14-foot plinth — a statue's base — and all are free to do whatever they want with the time.

Gormley said the 100-day event will reveal "the things we find funny, the things we find scary, the things we care about, the things we love."

The "One & Other" performance art — also broadcast live on the Internet — is the latest in a series of artworks to occupy an empty "fourth plinth" in the northwest corner of the square, which is also home to Nelson's Column and the National Gallery.

Rachel Wardell, a full-time mother from Sleaford in northeast England, was the first participant to be raised onto the plinth by a mechanical lifter. She held a sign promoting children's charities, and occasionally waved to people below. Afterward, she described the experience as "really relaxing."

Next up was Jason Clark, a 41-year-old surgical nurse from Brighton in southern England, who planned to stand, look around, take a few pictures and read a book if he got bored.

"I'm not a performer," he said. "I'm just up there representing slightly receding 41-year-olds.

"I think not actually doing something is pretty interesting — it will get people questioning what I am doing there."

Other participants have more ambitious plans. Elvis impersonator Mark Fitch, 39, plans to pay tribute to the King. Designer David Rosenberg, 41, said he will pedal a pink bicycle to generate electricity to light up his specially constructed suit. Student Heather Knight, 21, plans to wear a pigeon costume, and aquatic scientist Oliver Parsons-Baker, 26, said he will highlight the importance of clean water by dressing up as excrement.

Artist Suren Seneviratne, 22, was waiting his turn Monday dressed in a black-and-white costume with fuzzy ears.

"I'm meant to be a panda," he said. "My girlfriend made it for me."

Seneviratne said he was highlighting the plight of endangered species — "and actually, I just like pandas." He also planned to hold up a sign with his cell phone number, encouraging passers-by to phone him while he is atop the plinth.

Trafalgar Square was designed in 1838 as London's first public square and named for Adm. Horatio Nelson's 1805 victory over the French and Spanish fleets. A statue of the one-armed admiral stands atop Nelson's Column at the center of the square, and statues of other 19th-century military leaders are nearby.

The fourth plinth was built in 1841 for an equestrian statue that was never completed and stood empty for a century and a half. It has been occupied since 1999 by a series of artworks, including in 2005 the controversial sculpture "Alison Lapper Pregnant," of a naked and armless pregnant woman.

Visitors to the square Monday seemed intrigued by the human artwork. "I think it's wonderful," said Vee Wood, visiting from Wales. "It's a really inclusive idea."

London Mayor Boris Johnson praised the event as a "spontaneous and wonderful happening."

Unpredictability is part of the event's appeal — and a worry for organizers. A net has been placed around the plinth in case of mishaps or suicide attempts, and organizers are relaxed about the prospect that some participants may take off their clothes. The Web site carries a warning that it "may contain offensive content."

The unpredictability was illustrated Monday when an anti-smoking protester clambered atop the plinth minutes before the start time.

Stuart Holmes held a banner saying "Save the children — ban tobacco and actors smoking."

He descended after a few minutes, and Gormley accepted his intervention in the spirit of the work.

"I was worried that he might not leave," Gormley said. "But he did ... and that's lovely."