Moncton, CanadaKatsiaryna Artsiukh from Belarus, maintaining faith in her ability on a windy afternoon in the Stade de Moncton, lowered her World leading 400m Hurdles time for the year to 56.16.
But despite eventually winning by a clear second, the victory wasn't that straightforward as Evonne Britton and Vera Rudakova's highly motivated displays saw them clear leaders coming into the home straight.
However Artsiukh producing a blazing finish coming off the last bend managed to put a second of daylight between herself and Rudakova with Britton pushed down to third position.
Artsiukh admitted after finally getting past Britton and Rudakova in her sights: "I had my doubts if I could overtake her down the final stretch, but I just kept pushing and I am very happy that I finished first."
Rudakova the World Youth champion who had led for almost the entire race until Artsiukh late burst, caught her US rival 10m from the line to clinch second by 0.16 in a PB 57.16 with Britton also running the fastest time of her career.
Britton after bravely taking on the pace from the start, almost paid the penalty when Japan's Shiori Miki also made a late challenge to finish fourth in a National record of 57.35.
5000m gold remains in Kenya
Kenya's David Bett was never stretched after breaking away in mid race along with team-mate John Kipkoech and easily capturing the 5000 medal in a time of 13:23.76.
Bett after he and Kipkoech broke clear with six laps of the race remaining, finally claimed the gold medal for Kenya after the domination of their arch northerly rivals Ethiopian at the last two Championships.
Bett shared the pace with Kipkoech until the final 250m when sensing Aziz Lahbabi although 30m in arrears was hot on their tail, hit the front to win comfortably.
Kipkoech although tiring and being tracked down by Lahbabi, still had enough energy to finish in a PB 13:26.03 with the Moroccan posting 13:28.92.
"I was expecting to win," said Bett who was wary of Kipkoech. "I had no real plan, but I knew that my friend was very strong and I decided to run in front of him."
Bengtsson adds World Junior to World Youth title
Angelica Bengtsson added another gold medal to her already prolific collection when taking the pole vault title with a clearance of 4.25m ahead of Victoria Von Eynatten and Holly Bleasdale.
Last year's World Youth champion may not have achieved her ambition of breaking Silke Spiegelburg's World junior record of 4.48m or the Swedish senior mark of 4.51m, but it was still a victory to cherish.
Bengtsson after stuttering with a failure at 4.05m in round two saw herself temporarily trailing Victoria Von Eynatten at heights of both 4.05m and 4.20m, but triumphed with her first time clearance at 4.25m.
Germany's Von Eynatten finished runner up with 4.20m while the bronze medal went to Great Britain's Holly Bleasdale who vaulted 4.15m.
"I feel good," said Bengsston. "The height was not that good, but it’s a gold medal."
Bengtsson undeterred she didn't achieve any records, added: "The wind was blowing right from the side. But that actually didn’t bother me until 4.30m.
"It was only one jump that got affected, but I don’t know what happened. I will have to watch the videos."
National Junior record wins Hitchon Hammer title
Sophie Hitchon a former ballet dance became the first Briton ever to win a World Junior Championships hammer gold medal with the best throw of her life - another National record of 66.01m.
Hitchon didn't hang around when the competition got underway, her perfectly balanced frame unleashing the hammer out to 62.72m ahead of World Youth champion Barbara Spiler and world number two Li Zhang of China, who threw 58.68m.
The Brit team captain improved to 64.55 with Spiler just an ominous 10cm behind while Li Zhang threw 62.72m as the trio began to dominate the contest.
There was no change until round four when Spiler of Slovenia beforehand a strong candidate for victory, went ahead throwing 65.07 and in the next an even better 65.28.
But Hitchon who apart from a third round no throw was constantly over 60m, rsoe to the occasion and with her final attempt produced an unexpected success.
“I’m exhausted but so excited,” she said. “I got a bit tired between the middle two rounds but I knew I just had to go for it on my last throw.
“I thought after qualifying that I had a really good chance but I wanted to stay calm and just focus on the day because anything can happen in a final.
“The weather didn’t really help me because I’m not used to it being so hot. The fact that I was neck and neck with the Slovenian all the way through made it a really good competition and really drove me forward."
Hitchon watched by her grandparents, added: “I don’t think it’s going to sink in! The key is to save energy when you’re out here for a long time.
Gudzius the class of men's discus
Two weeks is a long time to wait through holding camp and into competition and people can get really uptight. If you stay calm it really helps.”
World leader Andrius Gudzius in second place behind Andrei Gag (61.85m) after the first round recovered to take the lead with 63.45m in the next and go on to score an expected victory.
The Lithuanian who threw 65.51m at the end of June proceeded to dominate the competition with further efforts of 62.49m and 63.41m before producing his winner of 63.78m in the fifth round.
Gag of Romania who improved his PB from 61.48m claimed second position with Australian Juklian Wruck taking third place thanks to a second round throw of 61.09m.
Both relay medals go to US
Back on the track, the United States women's team for the second time in 24 hours lowered their National 4x100 relay record streaking to victory ahead of Germany and the Netherlands.
The slick handling baton quartet of Stormy Kendrick, Takeia Pinckney, Dezerea Bryant and Ashley Collier, clocked 43.44 which was 0.12sec quicker than the previous night as they scored a fourth successive win at the Championships.
The Germans and Dutch also posted National records of 43.74 and 44.09.
The Great Britain team with the inclusion of Jodie Williams the 100m gold medallist, were expected to give the American's a race for their money.
But it ended in disaster when Williams running the second leg failed to take the baton cleanly from Rebekah Wilson and the team failing to finish.
The USA men's squad scored a fifth consecutive win achieving it in great style as they posted the World's second fastest ever time of 38.93.
Michael Granger, 100m silver medallist Charles Silmon, Eric Harris and Oliver Bradwell, roasted Jamaica and Trinidad and Tobago who nevertheless produced their best of the season with marks of 39.55 and 39.72.
Great Britain again lost out on a possible medal when almost at the spot where Wilson and Williams messed up their handover, Huggins and Talbot also managed to make the same elementary mistake.
Another World leader Robby Andrews running a near perfect race sent out a clear message he will be the man to beat when the 800m take place in the Stade de Moncton on Sunday.
800 and 110m Semis
Andrews paced himself easily around the first lap (53.72) where he was lying fifth, then going into the back straight gradually moved into contention with 200 to run and win with a fast finish in 1:48.76.
The NCAA indoor champion kicked off the final bend quickly establishing a clear lead as in a desperate finish behind him with a little bumping and barging, Morocco's Amine El Manaoui claimed second by 0.13sec in a season's fastest 1:48.83 from Ethiopia's Esrael Awoke who ran a PB.
However there were consequences for those involved in the fracas. Ireland's Mark Patterson and Awoke were disqualified for lane infringement 20m from the finish line and Manaoui red carded for obstruction.
The dismissals saw Grerat Britain's Niall Brooks advanced to the final as a fastest loser in 1:48.76.
Kenyan champion Dickson Tuwei with a solid front running display took the first qualifier with a PB 1:47.51 while Qatar's 1500m bronze medallist Mohammed Al-Garni slipped through on the inside past Samir Dahmani for second (1:48.15), the Frenchman making the cut as a fastets loser (1:48.31).
Casimir Loxsom suggested there could be an American 1-2 in the final. Hitting the front in the last 100m he won in 1:46.91. Kenya's David Mutua who had led until then was second in 1:48.04 with France's Pierre-Ambroise Bosse progressing as a fastest loser in a PB 1:48.38.
World Youth silver medallist Jack Meredith consolidated his position as 110m hurdles favourite with a meticulous semi final where he won in the fastest time of the day 13.53.
Meredith was even with Sam Baines at the seventh hurdle but then edged slightly ahead at the next of the Australian before powering home for a solid victory.
Baines his country's national champion and record holder finished in 13.66 to beat Norway's Vladmimir Vukicevic a serious medal contender and quickest in the heats by 0.01, who progressed as a fastest loser.
Frenchman Pascal Martinot-Lagarde another highly fancied for a podium finish, produced a lethargic display in his semi finishing 0.08 down on Greggar Swift of Barbados the winner in 13.65.
In the first semi Wataru Yazawa continuing what has been a good championships for Japan, sped off the last hurdle to achieve a PB 13.57 to beat US champion Caleb Cross who clocked 13.72 with Aussie Mitchell Tysoe (13.77) going through as a fastest loser.
Another World Youth silver medallist from Bressanone two years ago Aleksey Fedorova in the triple jump needed only his first attempt to surpass the 15.90m qualifier when leaping 16.47m.
The Russian who has a world class 17.12m under his belt this season, demonstrated that unless he under-achieves in Sunday's final he will end French domination of the event at the last two Championships.
Italy's Andrea Chiari along with Omar Craddock of the USA and France's Gaetan Saku Bafuanga Baya also went through automatically in Group B with Cuba's Ernest Reve and Alexandru Baciu doing so in the other qualifier.
Jamaica posted the fastest time in the women's 4x400m final a world leading performance of 3:32.30 to make themselves favourite to lift the gold medal in Sunday's final.
Their display in the second semi saw them hold off the Bahamas who set a National record of 3:33.50 and Nigeria which achieved a season's fastest of 3:34.81.
The first race saw Canada thrill the home crowd when roaring to a National record of 3:34.50 ahead of the United States and Russia who posted season's bests of 3:35.26 and 3:35.66.
In the men's contest the second round saw Great Britain set a world leader of 3:06.88 as they held off the challenge of Nigeria who with their quickest of the summer 3:07.17 beat Botswana comfortably by a huge 1.15sec.
The world lead didn't last long, the USA motoring around the track over a second faster in 3:05.84 as they soundly beat discarded the challenges of Japan and Jamaica despite those countries their quickest this year of 3:07.38 and 3:07.86.
Germany won the first semi in 3:08.79 from Poland and New Zealand who set their best marks of the summer with 3:08.80 and 3:10.83.
David Martin for the IAAF