The gold medal was won by Russia's Alexander Lesun, with Ukraine's Pavlo Tymoschenko taking silver and Mexico's Ismael Hernandez the bronze.
In the swimming heats, the first of Saturday’s events, fellow GB athlete Jamie Cooke set a new Olympic Record, finishing in a time of 1:55.66. Choong was not far behind, finishing third overall in 1:58.5.
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Choong finished the heats on 567 points in third place overall, with Cooke on 538, flailing in 18th.
Cooke clawed back a victory in the fencing bonus round to secure an extra point, as Choong chalked up two victories to remain in bronze medal position.
Into the show jumping round and Choong's fortunes could have been set to turn as he was allocated a double penalty point horse from Friday's competition, Verona. But perhaps better the devil you know than the unused Wuburga drawn for Cooke.
Choong took down the penultimate fence to score 293 as Cooke also knocked a pole as well as incurring some time penalties in the rain at the Deodoro Stadium to score 288.
GB's Jamie COoke sets new Olympic Record in the modern pentathlon swimming heats
Image credit: Reuters
In the final combined running/shooting round, Choong suffered in the shooting galleries and eventually finished ninth in his first Olympic games. Jamie Cooke finished in 14th.
No British man has ever medalled in the modern pentathlon competition at a summer Olympics, while British women had medalled at every Olympics (since the women’s event began at the 2000 Games) until this year. Samantha Murray finished ninth in the women’s competition on Friday while compatriot Kate French finished sixth.
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