MarrakechHarry AikinesAryeetey became the first sprinter in the six-year history of the IAAF/Maroc Telecom World Youth Championships ever to win both the 100 and 200 metres gold medals.
The 16-year-old Carshalton starlet having won the shorter race title on Thursday, powered to another magnificent victory over 200 metres in his final on Sunday night.
Aikines-Aryeetey at the Marrakech venue, turned the tables on Jorge Valcarcel the Cuban who although they were given the same time in their semi-final, was given the judges verdict.
On the occasion it mattered most, the Surrey sprinter showed without any doubt who was the better man, controlling the race from start-to-finish and winning in a world leading time for the year of 20.91seconds.
His constant lethal pace, saw him easily overthrow the challenge of Valcarcel and Matteo Galvan of Italy, although both rivals ran personal best times of 21.08sec and 21.14sec.
I just can't believe it
"I just can't believe," said Aikines-Aryeetey who after raising his hand with a Number One finger salute, spent a couple of minutes flat-out on his back after his outstanding performance.
"I just can't believe it, I was lying on my back on the floor before it really dawned I was world champion yet again," said the elated teenager.
The win saw him become the second British champion over the distance, following in the footsteps of 1999 winner Tim Benjamin who is now carving out an international career over 400 metres.
"I've no idea," said Aikines-Aryeetey of where he found the energy to run the fastest half lap of his life after six demanding races in five days.
He added: "Yesterday I was a bit tired but felt a lot better today. I ran a quick bend and I didn't really see anyone.
"My coach had told me hit the first 120 hard which I did. Then I saw the the Cuban alongside and just drove even harder.
"It's just amazing. I had so much lactic, I knew I was going to do something special and I just can't believe it that I ran 20.91sec," the first time he had dipped under the 21-seconds barrier.
Aikines-Ayreetey has been so focused on his preparations he was unaware that no-one had ever before achieved the demanding sprint double.
"I suppose I've made history," said last year's Commonwealth Youth Games runner-up. "But yes, I've got to be happy with two medals - who'd of thought it."
Abdulagadir Idriss proved the theory that breaking world leading marks in preliminary roundsa doesn't guarantee gold medals with a thrilling 400 metres hurdles victory.
Idriss might have won his heat and semi final with personal best times, but the Sudanese one-lapper did so without breaking the world leading time for the year with those victories.
Two of his opponents in their progress to the final had done so. David Klech of the United States achieved the feat twice while Saudi Arabia's Mohammed Dak did it in his heat.
But when it mattered most it was Idriss who went to the top of the table with a time of 50.78seconds - and to boot captured the gold medal with a nailbiting win.
Idriss most probably upset his rivals nerves when false starting in the opening track event of the final session of the highly successsful fourth World Junior Champions.
Then making them even more edgy after roaring from his blocks before the recall gun sounded, he slowly walked back to his lane five starting position.
Away at the second attempt Idriss led for the first hurdle before Klech came storming past and at one stage opened a lead of two metres ahead of the chasing pack.
But in the home straight he died and at the final barrier Idriss went ahead although in his determination to reach the line he nearly fell over.
Klech who had run himself to a standstill tried desperately to hang on for the silver medal, but a late dip for the line saw Dak given the verdict although both boys clocked the same time and pbs of 50.90sec.
Aymee Martinez was another to prove the theory that winning qualifiers means nothing, when beating 100 metres champion Bianca Knight with a relatively easy win over 200 metres.
The American was aiming to become the first woman ever to win both sprint gold medals at the same Championships - but her ambitions were aborted 50 metres from the finish.
At that point Martinez, Knight and Jamaica's LaToya King were evenly matched, until the Cuban winner went into a huge overdrive movement.
Martinez totally focused on winning the gold medal crossed the line in a Championship record and world leading time for the year of 22.99sec with Knight the fastest performer in both the heats and semi-finals recording 23.33sec.
King who had been consistent throughout the preliminary rounds finished strongly to post a personal best mark of 23.57sec.
The 100 metres hurdles produced a world leading time for the year from April Williams of 13.23 seconds as she bettered the previous fastest set by Natasha Ruddock and Manulea Galtier of France set the previous day, by one-hundredth-of-a-second.
Ruddock from Jamaica however had some compensation when clinching the silver medal in 13.38sec, splitting the winner and preventing a US one-two, ahead of Theresa Lewis who clocked 13.39sec.
A tactical 800m final saw Flavious Teresa Kwamboka after a slowish first lap of 64.39 seconds, use her sprinting speed to lead Winny Chebet to a Kenyan double.
Kwamboka's tremendous acceleration on the crown of the final bend saw her and her partner enter the final straight with only Katherine Katsanevakis trying to stay in contention.
The Aussie and Chebet with 50 metres remaining were fighting their own private battle - won by the African by 0.20sec in 2min 08.15sec - Kwamboka out in front of her own finishing in 2min 07.42sec.
There was a runaway win for Belal Mansoor Ali in the 1500 metres, the Bahrain middle-distance runner who has clocked a world youth's best-ever mark of 3min 33.86sec this summer, slaughtering his rivals.
Leading from start to finish, such was his superioity, the already beaten opposition settled for a private battle for the silver medal, won by Ali's teammate Bader Khalil Bader ahead of Sudan's Abubaker Kai.
Ali winner in 3min 36.98sec would almost certainly have blitzed the championship record of 3min 36.78 set set six-years ago by Isaac Kiprono Songok if the there had been someone to push him.
But so far ahead of Bader and Kaki who clocked personal best's of 3min 43.70sec and 3min 45.06sec, he missed the mark by just 0.20sec.
Yangsheng Yang won a first-ever pole vault title for China in a thriller ahead of the USA's Scott Roth both men breaking the 5.20m championship record set six years ago in Bydgoszcz by Sebastien Homo of France.
Yang who kept a clean sheet until the winning height of 5.25m won on countback, Roth having brought the bar down on two occasions. Albert Velez also matched the previous record to win the bronze medal for Spain.
Earlier Li Zhang kept the javelin title in Chinese hands clinching her victory with a second round effort of 56.66m ahead of Ukrainian Vira Rebryk and Yanet Cruz from Cuba.
Li Zhang was never under any pressure until Rebryk unleashed her best throw in the final round which fell just 40 centimetres short of the winner's mark while Cruz had a best of 51.66m.
Arantxa King improving her personal best by 25 centimetres was a shock winner of the long jump with the world's fifth best leap this year of 6.39m.
The Bermudan after lowly jumps of 6.07m and 6.06m, hit the board perfectly with her next attempt and with the wind exactly on the permissible two-metres-per-second limit, achieved an unexpected victory.
Eloyse Lesueur from France who has a best of 6.40m this summer, took the silver medal with a clearance of 6.28m while Romania's Cornelia Deiac improved her best-ever performance by just a centimetre, to claim the bronze with 6.25m.
The track programme rounded off with the medley relay, the United States winning the boys title with a world leading mark for the year of 1min 51.19sec.
The 100-200-300-400 split distances in the one kilometre race, saw them finish clear of Trinidad and Tobago and Saudia Arabia, the Caribbean and Gulf nations setting personal bests of 1min 52.51sec and 1min 52.89sec.
Just prior to their victory, the American girls quartet also set a world leader when taking the title with an easy victory in a time of 2min 03.93sec.
Australia in a thrilling finish, took the silver medals and Brazil claimed the bronze, both nations running their fastest times of the year of 2min 06.58sec and 2min 06.60sec.