In 2008 he finished seventh in 60 metres at the World Indoor Championships. That year, Williamson was featured in a BBC documentary called "Sprint", along with other 100 m hopefuls Pickering, Harry Aikines-Aryeetey and Wade Bennett-Jackson. Williamson represented Team GB in the 2008 Beijing Olympics in the 100 m and the 4x100 metres relay. He was second in the trials behind Dwain Chambers, running a new personal best of 10.03 seconds. However, following a minor injury at the team's training camp he was less successful in the Olympics. He failed to match his trials form and went out at the quarter-final stage. Together with Tyrone Edgar, Marlon Devonish and Pickering he also competed at the 4x100 m relay. In their qualification heat they were disqualified and eliminated for dropping the baton.