Guests invited to the £250-a-head charity gala include Sir Michael Caine, Dame Judi Dench, Danni Minogue, Delia Smith, Jenny Agutter and Ben Kingsley. Prince Charles has devised the Laurent-Perrier Harpers & Queen exhibit, The Healing Garden, which comprises plants with medicinal and culinary uses. He demonstrates 125 different species of tree, shrub and plant, including wild flowers, along with a curved limestone path leading to a shelter, made of earth and containing a hand-crafted oak and stone bench.