“The River Lark was known as Jordan, because people came from all over the Fens to be baptised by total immersion in its waters at Isleham.”

Look up the River Lark on Google image search and the first picture you’ll see is of a beaming fisherman, torch strapped across his forehead, holding tightly onto a huge, snake-like pike. You could say this clouds my mind as I ease my bike down the never-ending straight roads east of Ely. In fact, it’s all I can think of.

A sense of foreboding about this swim has hung over me all morning. The low, scudding cloud, which sends the temperature tumbling as my train pulls into the cathedral city, doesn’t help my mood either. I can’t imagine this solo jaunt into the waters of the Lark being much fun at all.

Having cycled six miles from Ely, through the village of Prickwillow and south across vast, intensively farmed cornfields, I turn off to reach the Lark via a track marked on the OS Map as Soham Tunnel Drove. This is around a mile or so downstream from Isleham, where Roger ‘swam with naiads’ in search of the place where East Anglia’s Baptists came for their full immersion experience.

I push my bike for the last 100 metres or so, over the rough ground of the levee which keeps the low-lying fields behind me from flooding. The track opens out onto a sizeable clearing. Despite the abundance of rubbish, from Burger King wrappers to burnt beer cans, there’s an overwhelming sense of isolation here. It feels as if nature has taken over this place. As I drop my bike, the only sounds are the occasional cries of a Great Crested Grebe and its chicks, sliding their way upstream and giving me the once over in the process.

My fears about this swim aren’t just about gnashing, 20 pound pike. Roger recounts having to negotiate huge reed beds and heaving himself out from chest deep banks, legs slick with black mud. Here though, the water at the bank is shallow, the perfect swimming spot. I slip on my wetsuit boots, keen not to have my toes nibbled, and slide quickly into the Lark. It’s knee deep, the sandy bed firm beneath my feet.

I push out to the central channel. The Lark here is around fifty feet wide. I test the depth by dropping my foot towards the bottom, only to find nothing. I kick on and swim upstream, increasingly aware of how far away I am from everything and everyone. The Fens feel more isolated and lonely than anywhere else I know in the UK. Perhaps it’s the flatness, but the sense of solitude is utterly overpowering.

Looking down, I notice the weeds billowing just below me. Pathetically, my thoughts return to pike and I turn myself back towards the bank and the safety of the shallows. I stay in a few minutes more, luxuriating in the fact I can’t see over the sides of this gorgeous river. The water is pleasingly chilly, the perfect temperature for a river dip.

I step back out onto the bank and realise my earlier sense of foreboding has slipped away, replaced instead by a keen awareness of the fact that this isolated spot is truly magical. As I get changed, a black-headed gull dive bombs onto the surface, flying off empty handed. Fish leap from the depths. And in the small reed bed I notice a reed warbler skitting around. As I try and get a picture, it darts off into the distance.

Otter spraint dots the bank too, the grass flattened to suggest the resurgent mammal uses this place as a regular spot to do its business. I yearn for a sighting, but am well aware of how shy they can be.

Instead, I push my bike away, past an old fence post etched with the legend ‘Back soon 2 tidy up’, and off down Soham Tunnel Drove. I wasn’t fully immersed here, but there is a sense of wonder on the Lark that is unquestionably ethereal. Getting in the river for just a few brief moments makes me feel as if I’ve been given the blessing of the local wildlife to share in its stunning space. I ponder this as I bump back along the track, off to reality under a gloomy August sky.