(Adds details, quotes)
By Ian Chadband
LONDON, Aug 8 (Reuters) - Pierre-Ambroise Bosse was such a surprise winner of the 800 metres at the World Championships on Tuesday that the Frenchman could hardly credit it himself.
The 25-year-old reckoned he had risked everything by making his move down the back straight.
"I'm a gambler, I love going to the casino and today I just gambled, I put everything on the red, even my last Euro," he told reporters.
Showing considerable resolve on the run-in, he proved too strong for the favourites - and hit his jackpot.
"Trust me. I live my dream. Or am I dreaming? I still can't believe it," the incredulous Bosse told the fans in the London Stadium after he held off fast-finishing silver medallist, Pole Adam Kszczot, for the first major gold of his career.
Teenage Kenyan Kipyegon Bett, who had made the initial move to break the field down the back straight on the second lap, just about held on to bronze after a tremendous late dash from Briton Kyle Langford.
The Frenchman held firm to win in a season's best 1 minute 44.67 seconds to Kszczot's 1:44.95 as the Pole, even with his familiar late charge, had to settle for the silver just as he had done in the last world championships in Beijing two years ago.
Bett clocked 1:45.21 with 21-year-old Langford setting a lifetime best 1:45.25.
Bosse, whose name has an acute accent at the end, always insists on people calling him "Boss" rather than "Boss-ay". Now it was evident why as he quite bossed the race over the last 250 metres.
In the same stadium where David Rudisha had run the race of the 2012 Olympics, breaking the world record with an astonishing 1:40.91 tour de force, this was an event hardly to be talked about in the same breath.
The opening lap involved plenty of rough-and-tumble with Nijel Amos, who had made a name for himself in that Olympic final when as a teenager he finished behind the great Rudisha in the third fastest time in history, particularly suffering.
He had been knocked out of rhythm twice as the field jostled for position and had to make his way to the front to get out of trouble as the field went through the bell in 50.76 seconds.
Bosse, who finished fourth in last year's Olympics, had not been the most fancied contender after a recent hip injury but having found recent form, was confident enough to shadow 19-year-old world under-20 champion Bett who pushed with 275 metres left.
Amos and former champion Mohammed Aman, the two major class acts in the field, looked as if they could be in the mix for the medals but proved nowhere near their best as Kszczot and Langford timed their final efforts with more aplomb.
"I did not have any race plan, believe me," said Bosse. "I just did it with feeling. I came to London and I was not in a very good shape. This is the best thing ever. I surprised myself, I surprised everybody.
"I achieved this victory with a lot of determination. It was with my mind, not with my legs and not with strength."
Kszczot was not totally happy.
"After the semi-final I was sure I could fight for the gold medal," he said.
"I made a small tactical mistake coming into the home straight. I could have started to speed up a bit sooner. I lost contact and that cost me the gold."
Bett said he tried to be inspired by Rudisha, who had been unable to defend his title because of injury.
"I was thinking about him before the race and I was hoping for any medal because of him," he said.
"So I am perfectly happy for this bronze as I wanted it so badly. In my first year as a senior, I could not hope for better." (Editing by Ed Osmond)