They're never going to listen to you - when you say, 'You really don't need a £1m Amazonian carved crystal bath', what they probably hear is: 'Manolo, Léger, Louboutin, Cavalli, Pucci: go! buy! now!' - but they might listen to people even richer than themselves. So call in Bill Gates and Warren Buffet, I say. They're busy making the world's wealthiest people hand half their wealth to good causes, so they might just get through to the girls. It is Christmas, after all.