Tweddle is the greatest British gymnast of all time, with three world titles and six European gold medals, and she will have two shots at an elusive Olympic medal - in the floor exercise and asymmetric bars.
It was on the latter apparatus that she became Britain's first ever gymnastics world champion in 2006. However, she lists the pinnacle of her career as winning the gold medal on the floor at the 2009 World Championships at London's O2 Arena. Drawn first to go in the eight-woman final, Tweddle electrified the home crowd with a near-flawless routine, which had the highest difficulty rating in the competition.
Tweddle initially planned to retire in 2006 but she will now try to become the oldest gymnast to win an Olympic title since Larissa Latynina, who was 29 when she won the floor exercise in 1964.
Tweddle suffered disappointment at each of her two previous Olympic Games. She failed to reach the asymmetric bars final in 2004 when a genuine medal hope, and four years later in Beijing she missed out on bronze by a mere 0.025 points after taking a step forward on her dismount.
She has since admitted: "It's still too sore to watch because it was just so close".
She failed to make the uneven bars final at her last ever World Championships in 2011.
Johannesburg-born Tweddle, who moved with her family to Cheshire when she was 18 months old, took up gymnastics aged seven at her local club, Crewe and Nantwich, but hated it!
However, her potential was soon recognised and she joined the British junior national team in 1994.
She gave up the vault and beam in 2009 due to recurring foot injuries.
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She has set up her own company, Total Gymnastics, with Steve Parry, the former Olympic bronze medallist in swimming, to help develop gymnastics in schools. She says: "I give teachers tips to plan lessons and help to make sure that children with talent get into clubs."