World junior 200 metres champion Delano Williams will represent Great Britain after switching allegiance from his native Turks and Caicos Islands.
The 19-year-old is now eligible to compete for Britain at the World Championships in Moscow in August.
Williams holds dual citizenship because the Caribbean archipelago is a British overseas territory.
His 200m personal best of 20.27 seconds, set this year, is faster than any Briton has run in five years.
Williams said: "I am very pleased that my transfer of allegiance has been confirmed and I am excited to be aiming towards a British team this summer."
He was eligible to compete for Britain at London 2012 as Turks and Caicos does not have a National Olympic committee and so cannot send a team to the Games.
He competed at the British Olympic trials last summer, but injury meant he failed to win a place on the team.
According to reports, Williams is so highly regarded that he has been asked to join Usain Bolt's Racers Track Club in Jamaica in October.