At the 2009 Birmingham Grand Prix Williamson won the 60 m and improved his personal best to 6.53 seconds. He was selected to compete at the European Indoor Championships in Turin and finished a close fourth in the 60 m final with 6.57 s. In the outdoor season in June, Williamson ran the 100 m in 10.09 seconds at the Fanny Blankers-Koen Games. This was the second fastest time by a European at that point in the season. Following this he finished second to world-leader Daniel Bailey at the ISTAF meet in Berlin; the first ÅF Golden League of the season. Williamson won his first national championships in July. He broke Dwain Chambers' domination of the British 100 m with a strong run into the wind. His time of 10.05 seconds was not a personal best, but it surely would have been had he not been hampered by a −1.8 m/s wind. Williamson was pleased with his first national title, having finished as runner-up a number of times, and turned his attention to a further Golden League meet against Usain Bolt. He did not repeat his national championships' form on the European circuit, running 10.14 seconds for sixth place at the Meeting Areva, although a fourth place at the London Grand Prix with 10.19 seconds into a strong headwind was an improvement. At the 2009 World Championships, Williamson failed to live up to expectations and was eliminated in the quarter-finals of the competition, recording 10.23 seconds after suffering a cramp. However, success came in the form of a relay medal, as he led off a team including Tyrone Edgar, Marlon Devonish and Harry Aikines-Aryeetey, and won the bronze, his first international relay medal. After the championships he took third at the Rieti IAAF Grand Prix, but finished last by some distance at the 2009 IAAF World Athletics Final. Although, he had won his first national championship that year, he had peaked outside of the major competitions. He stated that he was not sure how he had managed his 10.05 seconds win, but announced that he would return to Jamaica for a winter training camp to try to improve his consistency for the following season. He missed the 2010 season, including the 2010 Commonwealth Games, due to knee injury and surgery. He returned to Jamaica for rehabilitation but missed the 2011 season after the recurrence of an injury. In addition to sprinting, Williamson has also competed as a push athlete in bobsledding, and was selected as a member of the British team for the 2015 FIBT World Championships where he finished in 14th in the two-man event with Lamin Deen and eighth along with the rest of the British squad in the team event.
