Comeback for Chambers? – Sprinter Dwain Chambers, 34, tested positive for the designer drug THG in 2003. he was given a two-year ban from athletics and a lifetime Olympic ban. He was stripped of his silver medal won in the 100m relay at the 2003 World Championships. The bust also cost team mates Darren Campbell, Marlon Devonish and Christian Malcolm their medals. Chambers returned to competing in June 2006, winning gold in the 100m relay at the European Championships.
Millar divides team mates – Cyclist David Millar, 35, was banned after testing positive for the blood-booster EPO in 2004. In 2010 Millar won gold for Scotland in the Commonwealth Games. Fellow cyclist Sir Chris Hoy has spoken against lifetime Olympic bans being lifted. However, champion Mark Cavendish says he would have no problem with Millar in the team.
Blackpool Tower 'innocent' – Known as the 'Blackpool Tower' because of his giant frame, Carl Myerscough, 32, tested positive for anabolic steroids in 1999. The shot putter and discus thrower has always denied taking the drugs. He won bronze for shot put at the 2002 Commonwealth Games. Prior to the 2004 Athens Olympics, Myerscough appealed against his lifetime Olympic ban but was unsuccessful.
Priestly's drugs hurdle – Hurdler Callum Priestly, 23, won bronze at the 2009 European Athletics U23 Championships and at the end of the year was awarded lottery funding. This was pulled after he tested positive for the asthma drug clenbuterol in 2010. The ban expired in February this year.
Shot putters refuse test – Shot putter Kieren Kelly, 25, was third in the British rankings when he refused to take a drugs test in January 2010. The Olympic hopeful, from Newham in east London where the Games will be held, was banned along with fellow shot putter Jamie Stevenson, 22. Neither has returned to the sport since their ban expired in February.
Rakhra wrestles with return – Wrestler Rakhra Jatinder Singh Rakhra, 22, tested positive for anabolic steroids in 2010. The ban expired in February this year and he is believed to have returned to training. As a junior wrestler he was seen as Britain's great wrestling hope at the 2012 Olympics. However he was later beaten in the first round at the World Championships in 2009.