George Groves stops Francisco Sierra in sixth round

George Groves has extended his undefeated record to 15 bouts after overcoming Francisco Sierra with a sixth-round stoppage.

The 24-year-old's superiority was evident right from the beginning, although the contest was competitive until the Mexican hit the canvas in round six.

Groves landed a right-left-right-left combination and Sierra went down emphatically.

He returned to his feet and soaked up another flurry of punches before his corner threw in the towel with 45 seconds of the round remaining.