LONDON (AP) — Carl Froch knocked out British rival George Groves in the eighth round Saturday to retain his WBA and IBF super-middleweight titles in a rematch in front of 80,000 fans at Wembley Stadium on Saturday.

Froch floored Groves with a huge right hook with about 30 seconds remaining in the round, with the referee immediately stopping one of most hyped fights in the country’s boxing history. He improved to 33-2, with 24 knockouts.

Groves (19-2, 15 KOs) had started slower but grew into the fight, only to be knocked down with Froch’s biggest punch of the bout.

The rematch was ordered by the IBF after Froch’s win in a controversial first fight in Manchester in November.

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