Nelson wore down his opponent

Nelson knocked down May twice in the seventh round and was pronounced the winner after two minutes and 29 seconds of the round.

He sent May to the canvas with a right hook and then, after the German had got to his feet, repeated the trick.

The win was Nelson's 12th defence of his title.

Fighting your friend is like stabbing someone in the back Johnny Nelson

Nelson admitted that fighting his friend May had been difficult.

"Many times we have sparred in practice and because he knew me well he boxed totally different to what he normally does," Nelson said.

"He was an attacking fighter tonight and not a defensive one but that was what I expected.

"I was working on stopping him after nine or 10 rounds so I planned to make him tired after seven rounds.

"He was sharp, strong and determined and has a big heart but I had too much experience for him in the end."

Nelson immediately rejected any prospect of a rematch between the two.

"He is a good friend and fighting your friend is like stabbing someone in the back," he added. "But anyway this is business."