World No.1 Novak Djokovic has negotiated big-hitter Hubert Hurkacz to reach the fourth round at Wimbledon.

The defending champion dropped a set for the first time at the Championships to the 6ft 5in Pole, losing a tie-break in the second, on Friday.

It proved only a minor inconvenience, though, as the four-time winner surged through 7-5 6-7 (5-7) 6-1 6-4.

The only problem Djokovic faced in the first set was being told he could not wear his cap by the umpire because it contravened Wimbledon’s all-white rule.

It would be hard to find a whiter cap, frankly, and Djokovic had worn it during his second-round match, but apparently the black inner lining violated the strict dress code.

Djokovic duly played on cap-less and Court One was a server’s paradise until the Serb made the breakthrough in the 11th game, Hurkacz saving three break points but succumbing to a fourth.

The Pole was not going to go away quietly, though, and he fashioned two break points at 6-5 in the second, one with a Boris Becker-esque dive volley at the net.

Djokovic repelled both to force the tie-break, but another spectacular volley from Hurkacz helped him level the match.

Stung into action, 15-time grand-slam winner Djokovic broke to love twice as he raced away with the third.

A single break in the fourth was enough to wrap up proceedings, the 32-year-old coming through a decent test to safely make week two.

Earlier in the men’s draw, Argentina’s Guido Pella eliminated last year’s finalist and South African sixth seed Kevin Anderson 6-4 6-3 7-6 (7-4) result on Centre Court.

Tenth seed Karen Khachanov also exited following a 6-3 7-6 (7-3) 6-1 defeat to Spain’s Roberto Bautista-Agut.

Canada’s Milos Raonic entered the second week of the tournament after he dispatched American Reilly Opelka 7-6 (7-1) 6-2 6-1, with the 2016 finalist to next face Anderson’s conqueror Pella.