Clark holds big US Open lead as McIlroy makes back-nine stumble

Wyndham Clark holds a commanding four-shot lead at the halfway stage of the US Open, as Rory McIlroy lost ground after a rollercoaster second round at Shinnecock Hills.

Clark returned early on Friday morning to par the final two holes of an opening-round 64, following a fog-delayed first day, then mixed three birdies with two bogeys in a one-under 69.