“I pushed my soul in a deep dark hole and then I followed it in.” A line sung by the young Kenny Rogers in 1967, the summer of love, over a psychedelic haze of backwards guitar, feedback and acid trips. It brings to mind my first Dunwich Dynamo. If it felt like a journey into the unknown, that’s because it was. Where am I going? Will I make it? Who are all these people? Am I lost? Which way is the sea?

On my second and third Dynamos I spent long periods asking why I was back again, subjecting myself to the same discomforts of sleep deprivation but without the novelty to keep me going. By my fourth Dynamo I had begun to appreciate the familiarity of the ride, the places along the way and the faces in the crowds that were rolling alongside me. This year London’s best bike ride will celebrate its twentieth edition and I know something would be missing from my summer in the city if I didn’t join a thousand others all taking the same trip – an overnight bicycle ride from London Fields to the Suffolk Coast on the Saturday night nearest the July full moon. It’s a landmark in the cycling year and a good way of affirming that life should never be too serious for such a foolish excursion.

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As the earth turns away from the sun, a long stream of bicycle riders turn their wheels away from the city and embark on a practical education in the fine gradations of night. Just as the day divides into morning, midday, afternoon and early evening, nighttime sees evening fade into dusk and dusk into midnight. With each hour that passes I can’t help but become ever more closely attuned to the quiet stillness and subtle scents of the summer night. Midnight darkens to deepest night and – without warning – deepest night gives way to the dawn which heralds early morning and the bright light of a new day.

In the deepest recesses of the night, when all is quiet and you are alone on the road, savouring the thrilling feeling of stealing time, this is the moment to pull over, step off your machine and pause to appreciate the strange monochrome world you’re inhabiting. Take in the giant expanse of sky overhead, the stars peeking through the haze of the summer’s night and off behind, the orange glow of the metropolis left far behind. Scan wheat fields illuminated by the ghostly light of a hazy moon. Listen for the soft wingbeats of bats skydiving under the bows of the trees whose leaves shiver in a wind that sways the grasses too. Every sound can be heard with an unusual clarity. Now wait for the next group of riders to pass by. In the dead of night, the creak of metal and the turning of cranks, the ticking of freewheels and the long, sweet kiss of rubber on blacktop, all passing in an instant, makes for a sound like nothing I’ve ever heard before.

Good Company (detail) by Frank Patterson

A hundred and twenty gently rolling miles is enough to feel like a challenge for anyone, but not so far as to make failure any more than most remote of possibilities. If you’re unaccustomed to riding more than sixty miles in a day, then prepare with some outings to find out how a few continuous hours in the saddle feels. Whatever your physical capabilities, so long as you feel comfortable on the bike, can stay warm, and keep yourself fed and watered, you can be certain that you will make it to the beach.

Not least because there are few alternatives once it’s two in the morning and you’re feeling just about ready to pack it in. By this point it’s too far from home to turn back and the end is now closer than the beginning. But these are challenging moments. Entirely of its own accord, your pineal gland has been flooding your body with sleep drugs, making your mind muddled and slowing your metabolism so you begin to feel cold. This is when determination is put to the test.

A village hall ‘lunch stop’ is a welcome interruption to the nocturnal procession. It’s warm inside and the bright light, the food, the clatter and natter are a reviving stimulus ahead of the last dark, difficult miles before dawn’s grey fingers creep almost imperceptibly over the landscape.

Once the sun rises it’s a fast flat finish down to the Lost City. Today there are just a few houses, a pub and a café, but the Dunwich of the thirteenth century was an important seaport with thousands of inhabitants. A succession of huge storms redrew the coastline of southern England and washed it all away. You’ve ridden a hundred and twenty miles overnight to a place that isn’t there.

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My Dunwich Dynamo starts on my own doorstep but some riders travel from much further afield. Last year a Bike Show listener from New Hampshire, USA crossed the Atlantic to take part after hearing the radio broadcasts of past editions. If you’re a London cyclist who’s never ridden the Dynamo, it’s time to find out what you’ve been missing. To find out what condition your condition is in.

It’s just one night of three hundred and sixty-six nights in this leap year. One night to do something out of the ordinary and embrace the radical possibility of the bicycle. One night for a journey into the unknown that, wherever the dark places along the way, will end with the warm rays of the rising sun and the soothing waves of the salt sea.

Dunwich Dynamo XX is on Saturday 30 June 2012. Meet from 8pm at the Pub on the Park, London Fields. Find out more at Southwark Cyclists and book coach tickets back. A version of this article was first published on LondonBicycleCulture.com