Posing naked for Tunick, and 1,699 reasons for doing it

If anyone had told Jacqueline Donkin, a magistrate, a year ago that she was destined to appear naked on a 10ft-high mural plastered across a wall of Gatesheads' Baltic art gallery, she would have assumed that either they - or she - had consumed a few Newcastle Browns too many.

But Mrs Donkin, 44, who is also a civil servant, was there for all to see yesterday and pleased, on reflection, that she had made the decision to join 1,699 other people to take part in an installation by the American photographer Spencer Tunick at dawn on a chilly Sunday morning last July.

The huge mural depicts a sea of intertwined naked volunteers on their sides, some laying their heads on the hip of a naked stranger - including Mrs Donkin and a man who remains known to her only as "Rob".

"My husband is wondering what I am going to do next," admitted Mrs Donkin, as she was confronted by the mural at a private viewing for Tunick's participants yesterday. There was no sign of "Rob", with whom she had got on "rather well" - though she probably wouldn't have recognised him with his clothes on anyway.

The Rev Jim Craig, a chaplain for the arts in Gateshead, was equally sanguine. Nothing could compare with the sense of dread as he stood with his wife Annabel waiting for the call to strip off. "Everyone feels absolute fear waiting for the call to take clothes off," he said. "But there was a fantastic atmosphere."

The preview drew participants of every generation. Suzy Goulding, 35, who works in public relations, was "quite relieved" to find herself largely obscured, but her mother Gail, 54 - who had not yet arrived - was prominent. "That's fine. Mum took longer to come around to the idea but she's not stopped talking about it," said Ms Goulding.

Everyone had a reason for participating - Mrs Donkin had recently undergone major surgery and decided this was the chance to "start my life again". And it was simply an unmissable busman's holiday for a part-time life model, Nella Demkowicz, 42, from Todmorden, west Yorkshire, who persuaded her partner, Andrew Crowther, a carpenter, to join her. "We were just one homogeneous mass," said Mr Crowther, admiring a side-street image in which they are both highly visible.

Alan Tormey was the one individual who could say he had seen it all before. A serial Tunick participant, he has stripped off for the artist's 2003 installations in Barcelona and Santa Maria da Feira, Portugal, as well as Lyons in France and Central Terminal in Buffalo, New York, both last year. (Artist and subject are yet to run into each other.)

Mr Tormey took to "hiding behind lampposts" when he started out as a novice in Barcelona. "Then I started discovering so much about myself," he said.

"Every time I go out for a Tunick, I'm trying to recapture that sensation."