GrossetoAndrew Howe on home soil scored a resounding victory to add the World Junior 200 metres gold medal to the long jump title he captured two days earlier in Grosseto on Friday night.
Howe 19, born in Los Angeles but who came to Italy as a six-year-old, won by a huge distance of six metres to set a new Championship record of 20.28 seconds to the delight of the home Italian fans.
His performance ahead of South Africa's Leigh Julius who clocked 20.88sec and James Jamil from Jamaica who ran 21.00sec, struck a healthy 0.16sec from the six-year-old previous championships best.
Howe said: "I was aiming at the podium but before these Championships, the World junior title in the 200 metres was not on my mind.
"I am without words. I could not believe it," said Howe after seeing his winning time on the electronic scoreboard.
He admitted: "I would not have believed I could run the Italian junior record six months ago."
"When I won the Italian Junior Championships in Rieti in 21.11sec, I thought there was no point in coming here."
Never has any athlete achieved Howe's memorable double feat and his winning margin tonight was the biggest ever achieved over the distance in the 18-year history of the Championships.
World leader Kerron Clement and Brandon Johnson in a 400 metres hurdles race which went to the wire, both broke the two-year-old Championship record of Louis van Zyl.
Clement with one final lung bursting surge, ran 48.51sec the fastest time of his life just holding off his US team-mate whose time of 48.62sec was also the best of his career.
Ibrahim Al-Hamaidi trying desperately to stay with the American pair, finished in a Saudi Arabian record time of 48.94sec.
There was also a superb one-two in the pole vault for the German pair of Elizaveta Ryshich and Anna Schultze who both soared to personal bests to win gold and silver medals.
Ryshich was outright winner with a clearance of 4.30m - a 10cm improvement - while Schultze won on countback.
She vaulted 4.25m, the same as bronze medallist China's Yingying Zhao, the World leader this summer with a best of 4.40m.
Shalonda Solomon setting a personal best with a lightning burst of speed, easily won the 200m gold medal.
The American who flew past Jamaica's Anneisha Mclaughlin entering the final straight, struck a tenth-of-a-second from her previous best.
Her time of 22.82sec also took a healthy slice from the previous Championship record of 22.87sec, set by Jamaica's Veronica Campbell four years ago.
Mclaughlin finished runner-up with a season's fastest of 23.21sec with Shana Cox adding to Team USA's medal tally, clocking 23.63sec.
Aleksey Tovarnov set a world leader of 79.38m winning the javelin from Lohan Rautenbach of South Africa who threw a personal best 74.42m. Brazil's Julio de Oliveira was third with an effort of 73.86m.
Ronetta Alexander ran the fastest 100m hurdles time in the World this year of 13.28sec untroubled by runner-up Sabrina Altermatt who nevertheless clocked a Swiss record of 13.39sec, with Germany's Stephanie Lichtl third in 13.40sec.
Natalya Koreyvo proved far too strong for everyone of her rivals winning the 800 metres in a Belarusian record time of two minutes 01.47 seconds.
Koreyvo stifled the threat of last summer's European junior champion Simona Barcau, runner-up in a personal best time of 2min 02.23.
Behind the Romanian, Kay-Ann Thompson sliced 1/100sec from the 13-year-old Jamaican of Inez Turner, clocking 2min 02.67sec.
Andrey Azarenkov stood head-and-shoulders above his opponents, easily winning the hammer throw with a first round effort of 74.11m.
The Russian, third in last summer's European Championships, won ahead of Mohsen El Amany who ranks seconds on this year's World list behind him and Kamilius Bethke.
El Amany of Egypt had a best throw 72.98m with the German claiming the bronze medal with an effort of 71.91m.
Majed Saeed was a determined winner of the 800m in 1min 47.33sec - only 0.06sec in front of Kenya's Alfred Yego with Selahattin Cobanoglu third in a Turkish record of 1min 47.71sec.
Irina Petrova of Russia won the 10,000m walk. Last year's European champion finished in a personal best 45min 50.39sec,beating Zhang Nan of China (45min 58.54sec) and her colleague Vera Sokolova whose times was 46min 53.02sec.
Jessica Ennis leads the heptathlon overnight with a score of 3541 points. Lying behind the Briton is Lithuanian's Viktorija Zemaityte (3490pts) and Kathrin Geissler of Germany (3459pts).