With his gold and Olympic record in 4mins 02.95secs, Marchand left Japan's Matsushita Tomoyuku and the USA's Carson Foster well behind him. The promising 22-year-old, who broke Michael Phelps' world record in the 400 metres individual medley last year, is in phenomenal form. 

Marchand was a heavy favourite after demolishing Michael Phelps' 15-year-old world record. The trainer of Phelps is his trainer now. "It was almost like a football stadium but in a pool. Everyone was chanting my name, it was crazy," said Marchand.

Italy's Nicolo Martinenghi took gold for Italy in the 100m breaststroke final, ahead of Great Britain's Adam Peaty - who returns to the pools after taking time out to nurse his mental health problems - and the USA's Nik Fink.

In the women's 100m butterfly final, gold went to a thrilled Torri Huske of the USA and second place went to her team-mate Gretchen Walsh --she was the favourite, leaving China's Zhang Yufei in third. Canada's Maggie Mac Neil, defending champion, was fifth and Australia's Emma McKeon, queen of the pool in Tokyo with seven medals, was sixth.

Terminator Ariarne Titmus, defending 200m champion, returned to the pool a day after winning the 400m title ahead of Summer McIntosh and Katie Ledecky.  She showed no signs of fatigue and entered the semi-finals with the third fastest time, behind her teammate O'Callaghan (1:55.79).

Romania's David Popovici was the fastest in the men's 200m freestyle heats with a time of 1:45.65, ahead of Lithuania's Danas Rapsys and Belgium's Lucas Henveaux. Germany's Lukas Martens, who just won the 400m gold medal, also qualified for the semi-finals, as did South Korea's Hwang Sun-woo, the reigning world champion.

However, China's Pan Zhanle missed out, and by a long way, as the current 100m world record holder was almost four seconds behind. In other heats, South Africa's Tatjana Smith won the women's 100m breaststroke in 1:05.00, beating China's world champion Tian Qianting and Ireland's Mona McSharry.

American world record holder Lily King, gold medallist in Rio and bronze medallist in Tokyo, was fifth.  Hungary's Hubert Kos (52.78) led the men's 100m backstroke semi-finals. American Ryan Murphy, who won gold at Rio 2016 and bronze in Tokyo three years ago, was fourth fastest, while Italy's Thomas Ceccon, the world record holder, was 12th.

Palestine

Beyond the prizes, the participation of Palestinian swimmer Yazan Al Bawwab, competing in the men's 100m backstroke, was important in what was his second Games after Tokyo.

While he did not qualify him for the semi-finals, Al Bawwab hopes his presence on the world stage will highlight the plight of Palestinians who want to compete at the highest level of sport.

Al Bawwab swam with a small Palestinian flag painted on his chest and had family members killed by Israeli attacks. ‘I look like a boy from Gaza and the thing is that because of sport you listen to me and you care about what I say, but nobody cares about what the people of Palestine say, so this is my message of peace. Please treat us like human beings, we deserve the same rights as everyone else, and we want to play sport like everyone else,’ he said.

Swimming triathlon cancelled

The swimming part of the triathlon scheduled for Sunday has been cancelled after the quality of the river Seine was found to have deteriorated following the rains of the last few days, which affected the opening ceremony itself and is expected to improve in the coming days.