(Reuters) - Tom Watson stole the show from pre-tournament favorites Colin Montgomerie and Bernhard Langer to grab a one-shot lead at the U.S. Senior Open on Thursday after shooting a four-under 66 in the first round at Del Paso Country Club in California. The 65-year-old, who has won six senior majors as well as eight on the regular tour, braved searing temperatures to move ahead of a pack of six at three-under-par, including twice U.S. Open winner Lee Janzen and former Senior PGA Championship winner Michael Allen. Montgomerie got the better of Langer in their marquee pairing after shooting a two-under 68 to Langer’s one-over 71.