LONDON — When Tom Watson walks across the famous Swilcan Bridge at St Andrews for the final time, pausing for photographs to rapturous applause, the American's love affair with the British Open will come to a fitting end. The 65-year-old has been given an exemption to play at the spiritual home of golf next week to mark the 40th anniversary of his first appearance and his five victories in the championship. Watson, an eight-times major winner, dominated the British Open between 1975 and 1983, and the 1977 'Duel in the Sun' triumph over Jack Nicklaus at Turnberry is probably his most revered success.