In his first fight of the competition, the 29-year-old was often dragged into the close-range fight Cox favoured, but demonstrated his superior abilities with the powerful right hand to the body that ended Cox’s game challenge.
Eubank Jnr was ringside and is scheduled to be Groves’ next challenger in early 2018. Despite Cox suffering his first defeat, he showed he may also yet have a future in Britain’s most competitive weight division.
Both fighters demonstrated their aggression from the opening bell. Cox, recognising his finest chance of victory came in closing the distance between the two, was punished with several right hands from Groves but gradually also succeeded in catching the champion.
At the start of the second he trapped Groves in the corner and forced him to fight toe-to-toe, nullifying his greater power and variety and forcing him into a high pace, but after Groves escaped he landed with further powerful right hands.
Cox, accused by his opponent of not being a true middleweight and chosen by him at the competition’s draw, began to show signs of being broken down as early as the third, even if he continued to fight with both belief and intensity.
The one-time room-mates on the Great Britain amateur squad continued to exchange, but amid the better quality of Groves’ punching, the ending soon came. With Cox targeting the head and leaving himself open, the champion threw a big right hand to the 31-year-old’s body that instantly sent him to his knees, unable to meet the 10-count of referee Steve Gray.
There was earlier a stoppage victory for fellow British super-middleweight John Ryder, 29. In a largely one-sided fight, he had already knocked Denmark’s Patrick Nielsen to the canvas before brutally knocking him out in the fifth with three successive powerful right hands.