Justin Thomas started the British Open with a 3-under 68 at Royal Troon, showcasing resilience in challenging conditions, while U.S. Open champion Bryson DeChambeau struggled with missed putts and a 76 score. Rory McIlroy faced difficulties, including double bogeys, leaving him 7-over after the first round. Despite obstacles, Thomas maintained composure, finishing with birdies and impressive shots, leading the field early on. Justin Rose also performed well with a bogey-free 69 in tough conditions at Troon.