Sun’s rap sheet also includes clashing with officials over his affair with an air hostess, detention time for driving a Porsche SUV – that was hit by a bus – without a licence, and an altercation with a female Brazilian swimmer at last year’s world championships.

Along the way, Sun lashed the national anthem of China’s bitter war-time rivals Japan as “ugly”, and turned heads by pulling out of the 2015 world championships 1500m final, again citing a heart problem.

But no one would argue with the athletic achievements of the 1.98m Sun, 24, who is acclaimed as China’s most successful swimmer.

Sun became China’s first male Olympic swimming champion when he won the 400m and 1500m freestyle at London 2012, where he also lowered his own world record over the longer distance – after smashing Grant Hackett’s decade-old mark at the 2011 world championships in Shanghai.

The two titles in London put Sun at the forefront of his country’s best ever Olympic swimming performance, as China finished second behind the United States in the pool tally with five gold medals.

More glory could follow in Rio, although with China’s swimmers taking part in few international events, their form is hard to assess.

In London, China unleashed Ye Shiwen, then only 16, who won a sensational women’s individual medley double including a new world record in the 400m race.

Ye attracted doping innuendo – strongly rejected by China – after her final 50m burst in the 400m medley was quicker than American Ryan Lochte’s when he won the men’s gold a few races earlier.

China’s anti-doping procedures have also been in the spotlight ahead of Rio, after the World Anti-Doping Agency (Wada) suspended the accreditation of its national testing laboratory in Beijing in April.

In March, China’s state media had reported that six Chinese athletes had failed doping tests – including two who were let off with warnings for taking the banned muscle-builder clenbuterol.

Liu Peng, head of the general administration of sport, said in May that Wada’s suspension of the Beijing lab has brought “difficulties and challenges” for China’s anti-doping work, according to a Chinese media report.

Chinese swimming has a chequered reputation following a rash of doping cases in the 1990s. Seven Chinese swimmers tested positive for steroids at the 1994 Asian Games in Hiroshima.

In 1998, swimmer Yuan Yuan was banned after Australian customs officers discovered a large stash of human growth hormone in her bags at the world championships in Perth.

The towering Sun will be the most recognisable figure in China’s team, but his current form is largely an unknown quantity after he missed the national championships in April with a foot injury.

In June at Santa Clara, he won the 200m freestyle in a world-leading time, but then pulled out of the 400m final and the 1500m event without explanation.

It echoed last year’s world championships in Kazan, Russia, where Sun won the 400m and 800m but withdrew from the 1500m, blaming a heart condition.

Kazan was eventful for Sun, who was also involved in an angry confrontation with Brazil’s Larissa Oliveira in the warm-up pool.

Sun will hope for less choppy waters in Rio – although he may face a challenge from Italy’s Gregorio Paltrinieri, who swam the second-fastest 1500m in history at the European championships in May.

As for Ye, after her phenomenal 2012 Olympics, she failed to make the podium at either the 2013 or 2015 world championships, and was 22 seconds off her 400m medley world record at the Chinese championships, after suffering stomach pain.

However, Ning Zetao, who served a one-year suspension after testing positive for clenbuterol in 2011, should shine for China after he upstaged a strong field to win 100m freestyle gold at last year’s world championships.