KAZAN, Russia (AFP) - Britain's Adam Peaty said it was easy to break the men's 50m breaststroke record at the world swimming championships - after it fell for the second time on Tuesday alone.

South Africa's Cameron van der Burgh, the event's reigning world champion, had set a new record time of 26.62secs in the morning's heats, only for the 20-year-old Peaty to swam 26.42secs in the evening's semi-finals.

"I knew there was something in there, but I decided to just stay relaxed and enjoy the environment," said Peaty, who won the 100m world title by beating Van der Burgh on the wall in Monday's final.

"Semi-finals are a good time to do it, you don't have to worry about the medal places.

"It was great just to get out there and put a good time on the board.

"The 50m event is not an Olympic event, so there is kind of no pressure out there.

"That was a really good race, the heats were so easy, my time of 26.68secs this morning was probably the easiest 50m I have ever done.

"So I just enjoyed what I was doing in tonight's race."

Immediately after his morning heat, Van der Burgh had said the record would fall again and his prediction came true less than eight hours later.

It promises to be a breaststroke battle royal between the pair again in Wednesday's 50m final as Van der Burgh swam 26.74secs to win his semi.

Peaty's new world record is poetic justice for the Briton who had swam 26.62sec at the European championships in Berlin last August, but his time was not ratified by swimming's governing body Fina.