Triathlon Men's event rests on clean water result

In early May the mayor of Paris, Anne Hidalgo, the president of the Paris 2024 organising committee, Tony Estanguet, and other dignitaries officially opened a vast subterranean chamber near Austerlitz station in the south-east of the French capital.

- Jon Henley Paris

Measuring 30 metres deep and 50 metres across, the cathedral-like receptacle, its roof held up by 20 enormous pillars, took 42 months to build, at a cost of more than €90m (£76m). A construction worker, Amara Dioumassy, was killed in an accident during the build.

The Bassin d'Austerlitz spans 50,000 cubic metres - the equivalent of 20 Olympic swimming pools - and, after heavy rain, stores bacteria-laden stormwater that would otherwise end up in the Seine until it can be handled again by the sewage system. It is the centrepiece of a €1.4bn (£1.2bn) state and city-funded clean-up of the Seine under way since 2015 that is intended to make the river swimmable again by 2025, and its first big test was to be the Olympic men's triathlon swimming event.

For the time being at least, it has failed: after a 3.30am inspection on Monday (it takes 18 hours for the results to come through), Games officials yesterday postponed the triathlon until today - with no certainty that it would be possible even then.