Olympics Rio 2016: GB race walker disqualified for 'bent knee'

King was disqualified just before the halfway point while on target for a personal best time.

The rules of race walking requires the athlete to straighten their supporting leg as soon as it touches the ground - and to keep it straight until it has passed under the body.

There are officials on hand throughout the course to watch race walkers' form. They can issue a yellow paddle - which acts as a warning - or a red paddle if they are convinced the athlete is violating the rules.