He started off the 2005 Six Nations as a reserve in the opening match against Wales in Cardiff, but started the next match against France at Twickenham, where he scored a try in the 17–18 defeat. He subsequently started the remaining matches against Ireland, Italy and Scotland. He was a reserve in two other matches in 2005, against Australia and Samoa. Barkley dislocated his thumb in a club match against Leinster, the injury ruling him out of the opening game of the 2006 Six Nations Championship against Wales.