Chilled Lime and Watercress Soup

Although this is just a variation of the more usual lemon and watercress soup, the end result is quite different because limes have such a distinctive flavour. If you are serving it on a cold evening, just heat it up – it loses nothing by being served hot rather than chilled, and your guests will prefer a warming dish if the weather does turn inclement! On a proper fine summer’s day, this is a convenient first course for a dinner or lunch party, which can be made a day or two ahead and kept