Few artists could persuade thousands of people to get their kit off like photographer Spencer Tunick.The 40-year-old New Yorker is famous for his installations which feature large groups of naked people posed in artistic formations.Last May, he set a new record by getting a staggering 18,000 people to shed their clothes in Mexico City's main square - now the subject of an exhibition called "Tunick en el Zocalo".The turnout almost tripled his previous record of 7,000 people in Barcelona in 2003.Tunick has previously snapped groups of nudes in cities such as Bruges, Buenos Aires, Buffalo, Lisbon, London, Lyon, Melbourne, Montreal, Rome, San Sebastián, São Paulo, Caracas, Newcastle/Gateshead, Vienna, Düsseldorf, Helsinki, Santiago, Mexico City and Amsterdam.His models are volunteers who receive a limited edition photo as a reward.© Independent Television News Limited 2007. All rights reserved.