‘Enjoy your swim,” says Cleveland Pools chair Paul Simon, and a wave of spray rises from the water as a small tide of people leap into this historic open-air pool in the centre of Bath. Almost 40 years since it closed, the site is reopening after a £9.3m renovation – and these swimmers , selected in a prize draw, are the first in the water. When they come up for air, they break into applause.

Among them are Jenni and Alan Hinds, who came by bus from nearby Bradford on Avon. Both remember swimming here as children. “Getting dressed in the changing rooms brought it all back,” says Jenni. “I remember visiting with my brothers. It’s wonderful. I want to come all the time!”

Built in 1815, the Grade II-listed Cleveland Pools is the UK’s oldest public outdoor swimming pool. The country’s many revamped lidos were mainly built in the 1920s and 30s, so are whippersnappers compared with this one. Hidden from general view, the pools (there are two – a main 25m pool and a children’s splash pool) are set within a walled garden and reached via an unassuming footpath between two houses on a quiet residential street. The feeling of otherworldliness is enhanced by a caretaker’s cottage and changing cubicles shaped like Bath’s Royal Crescent in miniature, and the pools’ lagoon-like position along the River Avon.

Seizing the chance to splash about in a piece of living history, I swim up and down amid a starburst of refracted sunlight. After our sneak preview – and a sold-out Heritage Open Day appearance this Saturday – the pools will open for a short time this autumn and fully next spring. A sense of euphoria ripples through the water, such is the warmth of feeling surrounding the pools’ reopening.

Until the early 1970s, Cleveland Baths, as it was then known, was one of the city’s prime social hubs, and had been since 1901, when it was bought by the local authority and went fully public. Before then, although ostensibly open to the public, high subscription fees would have excluded working-class swimmers. A carefully segregated ladies’ plunge pool was included from the start, but the main pool was men-only and the first subscribers were all male, fostering a distinct networking scene (Bridgerton location scouts seem to have missed a trick here).

In Victorian times, one “Captain” William Evans, keeper of a pet baboon, was in charge of the pools and the site was as much about spectacle as wellbeing. Evans taught swimming and performed Houdini-style stunts, diving into the pool from 100 feet up, wearing an oversized top hat to cushion his entry.

Given the pools’ remarkable history it seems unfathomable that this Georgian wonder was once threatened with demolition, especially in a spa town that sells itself on heritage and watery wellbeing. Yet when the pools closed to the public in 1984, the site was used as a trout farm before being put up for sale by the council in 2003.

Fortunately, the development that would have seen the pools destroyed never materialised. After a long campaign by the Cleveland Pools Trust, and the backing of supporters, donors and funders (most significantly, the National Lottery Heritage Fund), restoration work finally started in May 2021. What had begun as a desire to preserve a piece of local history had, by then, become a mission to fulfil a need: dry robes may be as prevalent as reeds along the county’s riverbanks these days, as wild swimming continues to grow in popularity, but questions over water quality mean demand for outdoor swimming pools is also rising.

Knowing there would be demand helped see the trust through a renovation made more challenging by a lack of road access – materials all had to be brought in by river. However, visitors will be able to use this route next year when a riverside pontoon is added, rolling up by paddleboard, boat or (in keeping with the pools’ early users) sidestroke.

“Everything leads back to the river,” says project director Anna Baker, as we sit by the water’s edge. “Originally the pool was just a diversion of the river. Then we used the river for access during the build. The next step is to add a water-source heat pump and use the river to heat the pools’ water.”

Around the site today there’s a joyful, busy hum. It’s late September and the unheated-for-now pool water is a brisk 18C but, in the sunshine, it feels like being dunked back into summer. The changing room doors, painted a dapper seaweedy blue, flip open and shut as people bob in and out of the water. Children huddle under the hot, outdoor showers. Non-swimmers gather in what was once the ladies’ plunge pool to view a small exhibition. And the sound of splashing, laughter and conversation echo throughout just as they would have done 200 years earlier.

One person not in her swimming costume is Ann Dunlop. One of the three founders of the Cleveland Pools Trust, she’s watching the day’s proceedings from the terrace of the smart new cafe. “Today is a magic moment but I’m elderly and I have no desire at all to get in the water,” she says. “I’m not a keen swimmer but when the council put the site on the market for development it didn’t seem right. They didn’t know what they had. I could see the pools from my house so I couldn’t walk away. It was a constant reminder. We just kept going, kept badgering people.”

After 18 years of work, isn’t she just the tiniest bit curious to dip a toe in the water? “Next year, when the water is heated, I may be tempted,” she admits. She won’t be the only one.

Cleveland Pools will open this autumn (exact date tbc), with cold water swimming on Wednesdays and Saturdays (£6 adult, £4 child), then close for winter before reopening for the full season in spring. Swims will be timed, bookable sessions with a capacity of 200. From 2023, monthly swim passes and season tickets will also be available, clevelandpools.org.uk