Four women had to go to hospital after ingesting the substance, mostly used for cleaning, at Tiger Tiger nightclub on 7 December 2021.

They had suffered from burning in their mouths and vomiting.

A court heard the four women went to the bar for shots during a night out, and the barman realised he had run out of salt - a key part of having tequila shots, along with a lime slice.

According to Westminster City Council, the barman then made a concoction in an unlit storage area behind the bar, scooping what he thought was salt from a container into a plastic cup.

The court was told the women then licked the substance from the back of their hands and drank the shot.

It was at that point the barman knew something was wrong, with the court hearing the women became ill in front of him, leading him to tasting the white powder.

The council said he knew it was not salt by then, as his mouth and tongue burned, due to the chemical containing high levels of alkaline.

A3D2, which owns the club in the West End's Haymarket, pleaded guilty to four breaches of health and safety by "failing to ensure (customers) were not exposed to the risk of chemical substances", and were fined £120,000.

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Councillor Aicha Less, the council's deputy leader, said: "The shocking details of this case show a lack of attention and proper process for handling toxic cleaning chemicals.

"This incident shows that overlooking basic safety measures can have the most serious consequences.

"We hope the significant fine awarded in court acts to all businesses as a warning, preventing this from ever happening again.

"Westminster City Council's Health and Safety Team will continue to work with all businesses in the city to make sure the highest levels of health and safety are consistently maintained, and staff are educated in safe practice."