Foster rode his luck in the heats

Foster won the men's 50m freestyle in a time of 21.42 seconds after qualifying fastest for Thursday evening's final.

But Foster nearly did not make it that far after he was lucky to get through the heats.

Under new rules only two competitors from each country are allowed in the semi-final and final.

Foster, 33, finished joint 17th in the heats but made it into the semi-finals after a swim-off because only two of the three Germans who swam faster were allowed through.

"I only just scraped through this morning," said Foster after claiming gold. "I'm not really a morning person and I chilled a bit much in the heat.

"I always like to save as much as I can for the semis and the final.

"This has happened to me before, but the bottom line is that it's all about who is standing on the rostrum at the end of it."

James Gibson set a new championship record as he qualified for the semi-finals of the 100m breaststroke but Katy Sexton failed to make it through the heats of the women's 100m backstroke.

Sexton, who won the 200m backstroke title at the long-course worlds in Barcelona, trailed in fourth in her heat, which was won by fellow Briton Melanie Marshall in one minute flat.

Under the new two swimmers' rule, that meant Sexton failed to go through, with Sarah Price taking the other British place.

She was the second-fastest qualifier in the heats behind Germany's Antje Buschschulte.

The German men's team broke the 4x50m medley relay world record with Thomas Rupprath, Mark Warnecke, Fabian Friedrich and Carsten Dehmlow shaving .26 seconds off the old mark.

The Germans also held the previous record of one minute, 34.72 seconds.