Ivo Karlovic was at the centre of controversy in his 7-6 (7-3) 4-6 7-6 (7-2) 7-6 (11-9) Wimbledon triumph over Jo-Wilfried Tsonga on Saturday after a clear double-hit at a crucial moment of their third-round match.

Tsonga, seeded 13th and a two-time Wimbledon semi-finalist, had set point in the fourth-set tie-break to level the match at 2-2 when Karlovic stumbled forward for a volley and hit the ball twice on his way to winning the rally.

The 36-year-old Croatian ultimately prevailed to set up a potential meeting with home hope Andy Murray.

Karlovic took the first set in a breaker during a match that saw just one game go against the serve.

Tsonga claimed that solitary break in the fifth game of a second set that he eventually won 6-4.

The third-set tie-break went Karlovic's way, and the big-serving 23rd seed had match point at 6-5 in the fourth-set breaker, before the major talking point.

A double-hit in tennis is not illegal if it takes place as part of a single swing, but television replays suggested that Karlovic had actively changed the direction of his racquet in connecting with the ball for a second time.

He went on to win the point, and subsequently the match, becoming the oldest man to reach the last 16 at the All England Club since 1976.