Sprinter Dwain Chambers believes his presence at the Olympics should serve as a warning to anyone thinking of doping.
The 34-year-old was cleared to compete at London 2012 earlier this year when the British Olympic Association's lifetime ban on drugs cheats was overturned.
"I hope my presence makes people think twice and not do it," he told The Times. "I hope they never contemplate it because it really doesn't help.
"You may look at times and statistics but it doesn't help your life. It ruins your life and you will regret it for ever."
Chambers tested positive for THG in August 2003 and served a two-year ban.
He feels doping did him and his career nothing but harm - a fate he hopes other athletes can avoid.
"I got worse on drugs," he said. "It did not help me in any capacity. It made me a very unsociable person and ruined my career and the image of the sport.
"I hate to think I caused that. That is guilt."
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