Berlin authorities banned swimming in the Spree in May 1925 out of concern for public health.

Campaign group Flussbad Berlin, which is seeking to have parts of the river designated as safe for swimming, took direct action last week by inviting members of the public to take part in a protest swim.

City authorities said that, though swimming in the Spree is illegal, they would take no action against a protest.

Katrin Androschin from Flussbad Berlin told DW News: “We’re asking politicians to lift our ban. It’s about time.

“All the other cities are doing it – even cities like Paris prove that it’s possible. Cities in the Ruhr area, former industrial area in the west of Germany, proved it.

“New York has plans, London has plans, many other cities are already doing it and Berlin is really lagging behind.”

Paris authorities last month reopened the Seine for swimming for the first time since 1923 after a major clean-up ahead of the 2024 Olympics.