Buenos Aires - Argentine President Carlos Menem's visit to Britain this week is meant to show how trade can turn the Falklands War enemies into friends. Mr Menem arrives in London tomorrow for a six-day visit, the first official visit by an Argentine leader since 1960 and the first since the 1982 war over the South Atlantic islands. The president will get red-carpet treatment with lunch at Buckingham Palace and a speech to the Confederation of British Industry, an invitation rarely extended to foreign leaders.