Pierre-Ambroise Bosse took a surprise 800m gold as Britain's Kyle Langford just missed out on a medal and Nijel Amos finished in a shock fifth position.
Surprise final eight take to the track
Amos had gone into the final as the favourite for gold in the absence of double Olympic and World Championship gold medalist David Rudisha. Yet the 2012 Olympic silver medalist had been defeated by 2015 World Championship silver medalist Adam Kszczot as the pair closed out Ferguson Rotich in the first semi-final.
Rotich's failure to progress to the final was just one of a number of surprises in the race for a last eight spot. His Kenyan compatriot Emmanuel Korir missed out in the following semi-final, despite the fastest man this year, Thijmen Kupers, pulling out of the competition. Instead, it was Britain's Langford who followed Brandon McBride home despite almost being eliminated in the heats.
Kipyegon Bett qualified with the fastest time of 1.45.02 to ensure one Kenyan representative was in the final, ahead of 2013 World champion Mohammed Aman who recorded a season's best time. Bosse and surprise package Thiago Andre progressed from the same race as fastest losers.
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Bosse stuns the World
McBride hit the front off the break as expected, whilst Bett and Amos clashed as they jostled for position. McBride took the pack through the first lap in a rapid 50.76, closely followed by the two Africans.
Bosse made the first move on the back straight as he led Bett and Amos in a mini charge away from the group. Whilst Frenchman Bosse looked strong, Amos began to struggle and looked as if he was treading water.
Unsurprisingly, Kszcot finished strongly and hunted down the front three, closely followed by Langford as the pair made a late move from the back. Yet Bosse held firm to take an unexpected gold, whilst Kszcot passed Amos and then Bett to take silver.
Meanwhile, Langford continued to stretch but was phased out in a "bittersweet" finish as Bett just held on for bronze. Langford admitted after the race that he was "gutted after being so close to the medals".