Cucumber and Prawn Soup

Cucumber soup sounds such a good idea – refreshing, delicate, ideal for elegant lunches on the lawn – but the reality generally turns out to be at best faintly metallic, at worst one of the culinary blights of the British summer. Otherwise perfectly rational cooks, who would not expect to get carrot soup by grating carrots into yoghurt, or chicken soup by chopping cold chicken into cream mixed with a chicken stock-cube, nevertheless plough on with recipes that promise magical transformation