The home hope, who was one of Britain’s brightest medal prospects at the World Championships, raced off into an early lead in a bold attempt to dictate the pace of the final, but found herself overtaken late on by Kenya's Faith Kipyegon and the pre-race favourite, Sifan Hassan.
“I gave it everything I could,” she said after the race.
“I tied up in the last 15 yards. I gave it everything, considering the disruption I've had this year. I knew it was close. It happened so late in the race. I couldn't react, but I wouldn't have been able to because I was so tired.”
It was a fantastic race for Kipyegon, who added the world title to her 2016 Olympic gold. She judged her charge to perfection and was able to hold off the charging field over the final metres.
Kipyegon, silver medallist two years ago, took up the running with 600, to go and was stride for stride with Hassan until the Dutchwoman faded in the closing stages while the Kenyan stayed strong to cross the line in four minutes, 2.59 seconds.
Simpson, the 2011 champion, finished like a sprinter to take second while 800 metres specialist Semenya of South Africa grabbed the bronze.
Defending champion and world record holder Genzebe Dibaba, the Ethiopian who made the final only as a fast loser, was never in contention and finished last.
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