Watercress Soup

As well as forming a highly traditional and refreshing English summertime soup, watercress is reputed to be anti-ageing, reducing wrinkles and combatting free radicals. (Who are the free radicals? Why is their main policy to make people look older?) Personally I think the main ingredient to looking good over 40 is to have lots of money, plenty of holidays and to drink olive oil by the gallon. But if watercress soup will help, who am I to argue? Serve this in teacups, either chilled or warme