“I had entered a swimmer’s dream. People lolled half-submerged along the top of the weir, reading or sunbathing, while others paddled themselves in coracles, swam, dived, or just sat about in bathing costumes.”

Led upstairs, through a warren of corridors and into the first-floor drawing room, the mill window is flung open. As the first of our three-man group throws himself forward and hurtles towards the water, my stomach lurches. Eased up into the window frame, I peer down. I’d thought it was a straight drop into the drink. Yet it turns out I need to clear a four foot path before breaking the surface.

Closing my eyes, I leap forward, crashing into the Avon. As I surface, a cheer and round of applause erupts from the dozen strong party on the bank. “You made it by about 4-inches,” says John, the most fearless teenage swimmer I’ve ever met.”Good effort.”

This is Cropthorne Water Mill in Fladbury. I’ve been invited here by John’s dad, George. His cousin, Judith, invited Roger to swim here when he was writing Waterlog. The mill has been owned by the family since 1905, and was rented by them for 20 or so years prior to that. Situated on an island in the Avon, its reached by a small ferry attached to a pulley, traversing the river next to a large weir.

There are 15 of us here today, and the air of adventure is palpable. Having hauled myself clear after my window jump, I take a seat around the large outdoor table as George and his friend Mark start talking about building a tower on the ferry. I’m unsure as to how this will work until I see them taking down a three-metre high scaffold on the bank, carefully reconstructing it on the teetering vessel.

Soon we’ve all clambered aboard, one by one the large group of kids climbing to the top of the makeshift rig and diving off impressively. The ferry rocks each time. I’m last up, my childhood fear of jumping into water, especially from a height, rearing its head as I reach the top plank. I go for a rather ungraceful flop forwards. It’s a pathetic effort considering the talent on show.

Swimming has been a way of life at the mill for years. Mark tells me he used to come here as a kid and indulge in exactly the same kind of stunts we’ve just pulled off. “It was always something that bordered on the dangerous,” he says. The walls of the mill are lined with pictures of people lolling in the water and everyone here today gets in at some point for a dip.

Roger’s visit here was the result of a letter the Environment Agency (EA) had sent the family, warning them about the dangers of swimming in the river. Weil’s disease and ‘dangerous currents’ were the main themes. I ask George if they still have any trouble from the EA. Apart from an attempt to string oil barrels across the weir to stop people falling down it a few years ago, they’ve gone quiet. He puts this down to the fact they have the somewhat more important task of improving flood defences to handle.

The family are keen that I do as Roger did, so before a tour of the mill, I’m given a coracle to pilot. I’m told it’s a larger one, so I won’t end up falling out. The figure-of-eight paddling proves beyond me and while I manage to go backwards, I need to be rescued and towed back to dry land by one of the mill’s rowing boats.

After lunch, I slide off from the weir wall for a swim upstream. I’m pointed in the direction of a bridge about half a mile away (where Roger swam to on his visit). Instead, I pootle along to a cedar tree on the far bank, past back gardens and the odd flotilla of ducks. I turn on my back and look back towards the mill. It’s a scorching hot summer’s day. In the distance, the water is alive with people.

This is what I imagine Roger felt when he came here and wrote about ‘swimming being enhanced by company, and sometimes by solitude’. As I breaststroke back towards the weir and its convenient underwater ladder, the Vale of Evesham around me, I feel I’ve managed to strike on the perfect balance of company and solitude here at Fladbury. Every type of swimming is catered for.

Later, as George drives me back to the station at Evesham, he tells me that few people other than his extended family swim in this stretch of the Avon. Worries about pike, or a bad stomach, seem to prevail. It seems a pity, but then I can’t help but feel this watering hole needs to be kept for wild swimming fanatics only.