Celebrities have always captured the imagination of the public. In today's age of consumerism, their ability to influence our behaviour can be seen worldwide. Harnessing this power can reap huge rewards for business -- the Jamie Oliver campaign helped turn around Sainsbury's fortunes, with the return on investment estimated at 27.95 for every advertising pound spent; sales of Walker's Crisps increased by 105% thanks to Gary Lineker; One to One...