The relay successes came after the previous night’s wins in both 4x100m sprints and saw the USA become the first country to claim all four relays at the same championships.

Allyson Felix was a revelation, a stunning burst of speed on the second 400m leg after taking over from DeeDee Trotter setting the side up very early for victory.

With Mary Wineberg and Sanya Richards maintaining the momentum, the side clocked the fastest time in the world this year at three minutes, 18.55 seconds.

That wrecked the hopes of Jamaica and Great Britain although both countries posted national records of 3min 19.73sec and 3min 20.04sec.

“It’s great to work together,” said Felix, who added to her 200m and 4x100m relay gold medals.

“I ran a very strong leg, but I wasn’t sure where I was compared to others.

“It was my first time running the (400m) relay and it has just been amazing.”

The men posted the third fastest time in history at 2min 55.56sec and finished well clear of the Bahamas and Poland, who responded with marks of 2min 59.18sec and 3min 00.05sec.

LaShawn Merritt and Angelo Taylor, the individual silver and bronze medallists, opened a huge gap of over 20 metres on the first two legs.

Darold Williamson did lose some ground before handing to his training partner and individual 400m champion Jeremy Wariner, who was never troubled on the final circuit.

“The other guys put it right before me and I just got it home strong,” Wariner said.

“We had the the top three for the quarter, so we were dominating the relay.”

Lagat, winner of the 1500m title in midweek, set the ball rolling for the Americans, taking the 5000m crown to become the first man to achieve the double in championship history.

The opposition in a slow race played into the hands of the Kenya-born star who became a US citizen three years ago.

Lagat, representing the USA for the first time, was set him up for an easy win even after Britain’s European silver-medallist Mo Farah injected something much quicker 700m from the finishing line.

Farah led until the final 200m when Kenya’s former champion Eliud Kipchoge and Moses Kipsiro of Uganda went past, tracked by Lagat.

Lagat produced a decisive sprint for the line, winning in 13minutes 45.87seconds – the slowest time in championship history.

Kipchoge claimed the silver medal clocking 13min 46.00sec with 20-year-old Kipsiro third in 13min 46.75sec.

Javelin gold medallist Tero Pitkamaki made amends for failing to make the podium when number one in the world two years ago on home territory in Finland.

Pitkamaki, fourth in Helsinki, took the lead with a throw of 89.16 metres then unleashed a mighty 90.33m to claim the gold ahead of Norway’s Andreas Thorkildsen and USA’s Breaux Greer.

Alfred Yego pipped Canada’s Gary Reed on the line to win the 800 metres title by the thickness of his vest.

Reed, who led from gun-to-tape, appeared to have the race tied up until he tired and his Kenyan rival snatched gold from his grasp.

Yelena Soboleva led from the beginning of her 1500m and the fastest woman in the world this year appeared confident enough to win her first championship medal but was overhauled in the last 150m by Bahrain’s Maryam Jamal.

Blanka Vlasic won Croatia’s first championship medal, taking gold in the high jump.