Former world champion Anthony Joshua needed seven rounds to stop stand-in opponent Robert Helenius in the seventh round of their heavyweight bout on Saturday.

Helenius was only drafted in after fighting in Finland last weekend when Dillian Whyte was ruled out of what would have been an all-British clash following adverse analytical findings in a doping test.

The 39-year-old Helenius, who entered the ring with 32 wins and four defeats from his 36 professional bouts, was knocked out in the first round by Deontay Wilder in October.

He avoided a repeat of that embarrassing reverse on Saturday although, with Joshua making a cautious start, boos rang out from a capacity crowd at Londons O2 Arena during the third round.

Joshua, however, landed with a left hook and then hit Helenius with a right to the face later in the round.

The local hero rocked Helenius again in the fourth before the Finnish veteran caught Joshua with a jab.

But the fifth round left Helenius with a bloodied nose and although Joshua made him stumble with a left uppercut, he survived and got through an uneventful sixth round.

Joshua did give his fans what they came to see when he knocked out Helenius with a powerful right-hand punch in the seventh. (AFP, but headline rejigged)