Anthony Joshua floors Kevin Johnson in the second round

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Kevin Johnson was supposed to provide Anthony Joshua with his toughest test yet in the professional ranks, but he ended up like the rest: On the canvas.

The 2012 Olympic gold medallist stopped Johnson in the second round after twice flooring the American in the opening round at the O2 Arena in London.

Johnson (29-7-1, 14 KOs) suffered his first stoppage defeat in 37 fights as British heavyweight hope Joshua improved his perfect professional record to 13-0 (13 KOs).

Johnson, 36, might not be the force he was in 2009 when he took Vitali Klitschko the distance for the WBC world heavyweight title, but he had denied the likes of Joshua's fellow Britons Tyson Fury and Dereck Chisora stoppage wins in the last three years.

Joshua, 25, has never been beyond three rounds in the paid ranks and he did not look he would be taken into unknown territory after a totally dominant first round.

Joshua did not hold back in the first round and floored Johnson with a right at the end of fast combination. No sooner had Johnson hauled himself up than he was nailed to the canvas again by another flurry of hooks.

Johnson, who had not fought for a year and has now lost five of his last six fights, was saved by the bell but it took Joshua 83 seconds of the second round to overwhelm the American before the referee sensibly stopped it.

Watford-born Joshua will fight again in Manchester on July 18 with potential domestic fights against David Price and Dillian Whyte later in the year.