Great Britain's former Olympic and world 400m champion Christine Ohuruogu has retired at the age of 34.
Ohuruogu won 400m gold at the 2008 Olympics in Beijing a year after becoming world champion in Osaka.
She took silver at the London Olympics in 2012 before regaining her world title in Moscow in 2013.
"Today is the start of the British Championships and as I won't be competing I feel it is a good time to announce my retirement," she said.
"I didn't feel ready to retire after last season but a combination of my studies and a niggling injury restricted how much training I was able to do this year."
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The east Londoner was given a one-year ban for missing three out-of-competition drug tests in 2006 and her participation in the Beijing Games of 2008 was under threat at one stage from a British Olympic Association bylaw that meant any doping offences were punishable by lifetime Olympic bans.
Ohuruogu, who became an MBE in the wake of her 2008 Olympic triumph, was the first British woman to win two athletics world titles.
"I end my career with four Olympic medals and five World Championships medals," Ohuruogu said.
"Athletics has been my passion for so long and I am proud to call myself an athlete."