A popular London lido was forced to close on Tuesday after a fight broke out amongst swimmers over the sweltering Bank Holiday weekend. The registered charity that operates Parliament Hill lido in Hampstead Heath condemned the “unacceptable behaviour”, which led to its closure until Wednesday. It is understood that the fight broke out Monday evening, with the Evening Standard reporting that an individual had been struck on the head with a bottle. A notice on the website reads: “The Lido is closed today following an incident yesterday. “We expect to re-open tomorrow. Lido season ticket wristbands will be accepted at the Bathing Ponds today. “We expect the Bathing Ponds to be very busy.”On social media, it was reported that swimmers had queued for up to an hour and 40 minutes as increasing numbers of Londoners sought a respite from the 35 degree heat. One cafe user noted that the clientele often changed during heatwaves, and said: “They didn’t do body searches. People should have been searched. The security seems to have been really light.The City of London Corporation said it was ‘unacceptable behaviour’ (Chris Seymour)Parliament Hill Lido is a 60-metre long open-air, unheated swimming pool which is open 365 days a year, and was first opened in 1938. The pool has a maximum capacity for 3,000 bathers each day, and attracts around 160,000 visits annually. A City of London Corporation spokesperson said: “We condemn the unacceptable behaviour that led to the temporary closure of the lido on Bank Holiday Monday.“Following an altercation involving a small number of individuals, we took the decision to close for the safety of our staff and the public. The Metropolitan Police Service attended and are investigating. We will reopen as soon as it is safe to do so.”It comes after large crowds of swimmers have been accused of disturbing swans and their chicks in Hampstead Heath. Nine people, including seven teenagers, have died after getting into trouble in the water during this heatwave.The Royal Life Saving Society issued a plea for everyone to “stop and think” before getting into the water in response to the deaths, most of whom were children.It noted that “warmer weather unfortunately correlates to an increase in accidental drownings” and that despite warmer air, “water temperatures remain very cold”.