Gormley's art begins with gatecrasher on top of fourth plinth

Now, for the next 100 days, all it takes is a lucky bid and a comfortable pair of shoes. Or, in the case of one sneaky protestor, an athletic leap and a lax sense of security.

"How the hell did that happen?" muttered a security guard as Stuart Holmes, an unemployed man, armed with a home-made banner, managed to upstage the carefully managed opening of Antony Gormley's public art project and clamber on to the plinth before the first official participant could be hoisted up.

While another security guard cried "Stop him", the Mayor of London, Boris Johnson – who was there to help launch the art project that will see ordinary members of the public spend one hour each, 24 hours a day, for the next 100 days on the plinth, until 14 October – could only look on with admiration and declare: "Now, this is art!"

For Mr Holmes, who has dedicated his life to campaigning against actors smoking in films, it was publicity. He unfurled a banner that read: "Save the children. Ban tobacco and actors smoking."

Antony Gormley, the artist behind the Angel of the North statue, thanked Mr Holmes for his contribution, describing him as "the warm-up act" and asked him to come down so that Rachel Wardell, the first of 2,400 official participants, could take her place.

The crowd of around 100 applauded when Mr Holmes finally climbed down and was replaced by Mrs Wardell, who had chosen to stand silently holding a lollipop stick marked with the telephone numbers for Childline and the NSPCC.

Second on the plinth was Jason Clark, 41, an NHS nurse from Brighton, who mostly stood still for his hour, occasionally waving at the crowd and taking photographs as he wanted to represent an ordinary British man. After, he said: "The first five minutes I was quite nervous. After that it all seemed serene."

The bright and sunny weather was shattered by a sudden downpour which pelted Jill Gatcum, a 51-year-old IT consultant from London, as she released 60 helium balloons which were sponsored by friends to raise money for her favourite charity.

Christine Sharman, 54, an adult education worker from Wakefield, West Yorkshire, the fourth official participant, took a laptop computer and a placard with a picture of a hen and a hawk on to the platform which measures 5ft by 14ft and is around 23ft high.

"Boring!" shouted one heckler at Scott Illman, a bar owner from Hammersmith, who dressed as a town crier and spent his hour on the plinth promoting his businesses. Afterwards he said: "My little heckling friend did throw me for a bit."

Among the spectators was Madelyn Cruickshank, 63, a bookshop worker from Inverness, who said: "It's a very good idea. It will be interesting to see what kind of people go up there. They can do anything they want, so that will be fun."

Art student will be boating for her hour of plinth time

A SCOTTISH art student is basing her exhibit on the Fourth Plinth on a boat she was given by her sculptor father.

Collette Rayner, 19, who is about to begin her second year of studies at Glasgow School of Art, takes her place for an hour tomorrow at 6am.

"I love art works. I think Antony Gormley's a really great artist, his work is really brilliant in that it involves the viewer, the public," she said.

"It's such a great idea, instead of having a typical statue, I'm so pleased to be involved, I'm very nervous, but I'm looking forward to it."

Ms Rayner said she's struggling to stick to one idea for the plinth but wants to do something related to water transport.

Her father, the Fife journalist and sculptor Martin Rayner, died in 2004. Living at the mouth of the Tay, he centred much of his work on the sea and the water.

"I have a boat that I inherited from my dad. It's a rowing boat, that sits in my garden. Aesthetically it's a really beautiful boat. I wouldn't take it with me but I might construct something boat-like, an image of a boat."

She may row on the plinth, going slowly to make a point that everything needs to slow down in the rush-hour, she said.