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One of the oldest and most contentious records in athletics is 30 years old.

On 6 October 1985, East Germany’s Marita Koch ran the 400 metres in 47.6 seconds. That's more than one-and-a-half seconds quicker than Allyson Felix clocked to take gold in the 2015 World Championships.

Koch's record has been the subject of much debate over the years. No-one has come close to breaking it - and Koch competed in an era when East Germany was known to be systematically doping its athletes.

She never failed a drugs test and she has always insisted she has done nothing wrong.

(Photo: Marita Koch / Credit: Getty Images)