Emmanuel Macron’s promise to strip off to his Speedos and swim in the Seine to prove it is safe for athletes has yet to be delivered. The Olympic Games commence in July and the river remains essentially a sewer. Although the water quality is supposedly getting better as the rains are relenting, Macron is wise not to hurry.

Diarrhoea in the Olympic Village may be the least of the problems, even if the athletes complain

In addition to fears that the Paris games will attract terrorist attacks, there is the now the unpleasant prospect of athletes being infected with norovirus and other unfortunate ailments of the intestinal tract. Not that London can offer any lessons after the Boat Race in which crews were required to compete in filthy water with predictable consequences.

The Surfrider Foundation, a water-focused NGO, has been testing the Seine since last September and has so far completed 14 samplings of water quality under the Alexandre III and Alma Bridges, where Olympic open-water swimming events are planned.

In February, levels of E. coli in the Seine were multiple times the limit set by World Triathlon, the international governing body for the Olympic sport. ‘I wouldn’t recommend swimming in the Seine river right now under any circumstances,’ said Dan Angelescu, chief executive of Fluidion, a water-monitoring company working with the city.

Although there is a great deal of ambivalence and even hostility to the games amongst Parisians, many await with keen anticipation the president’s diving into the Seine, not least because of the obvious scope for comparison with Chairman Mao Zedong’s 1966 plunge in the Yangtze.

Mao’s immersion near Wuhan launched the Great Proletarian Cultural Revolution, much as Macron wishes to launch his own vision of the rebirth of Europe. Mao was demonstrating physical prowess, for the battle ahead. Athleticism has also been a preoccupation of President Macron, seeking to re-establish his authority following the loss of his majority in the National Assembly and anticipated terrible results in forthcoming European elections. Macron the policy nerd is relaunching, in Rocky Balboa mode, biceps bulging.

Will Macron go through with it? He’s not the first politician to make such a promise nor would he be the first to break it. Paris mayor (subsequently president) Jacques Chirac said in 1990 that he would turn the Seine from a sewer into a river clean enough to swim in, and prove it himself. His swimming suit never got wet.

The Olympics are an event of overarching significance for President Macron, offering a global stage for him and France and Paris to produce a bold, original and thrilling event, and a splendid distraction from all that has ailed his presidency. If nothing else, it makes him a centre of attention this summer. But the risks are immense and following the attack in Moscow some might say reckless.

On July 26, the Seine will be the focal point for an opening ceremony that has the security services seized with anxiety. Athletes on boats will float past hundreds of thousands of spectators. A gigantic security operation has been planned. Police leave has been cancelled. But the area that has to be secured is immense, with the risk of attacks also outside the security perimeter. It’s going to be a big test, in a city with a long tradition of terror.

Diarrhoea in the Olympic Village may be the least of the problems, even if the athletes complain. ‘We need a plan B,’ Brazilian swimmer Ana Marcela Cunha, the reigning Olympic open water champion pleads. ‘The Seine is not made for swimming.’ So far, there is no sign of any such plan. A huge new sewage holding tank is to be opened in May, which the environmental engineers think will make a huge impact. French authorities are confident they will deliver a clean river after more than 100 years in which swimming has been forbidden. Perhaps they will. Marc Guillaume, prefect of the Île de France, Macron’s personal representative in the capital, promised again this week, ‘Olympic athletes and Parisians will be swimming in the Seine this Summer. I will.’

Time will tell.