Last week I went Mudlarking for the first time. I’d known about this curious riverside activity for a while but had never got further than thinking: ‘I wonder how they get down there’, and following one of them on Twitter.

Maybe twenty years of living in a city without a river has made me treat real ones (rivers not cities) with near mythological reverence – I deliberately seek out the courses of ‘lost’ rivers when visiting London and even finding the Thames from London Bridge usually involves several wrong turns, elevation miscues and back alley shuffling. From one point on my most recent ‘lost Thames’ re-orientation, I saw a sealed-off set of concrete steps leading down to the river bank itself; once I reached the walkway I found there was no easy way in.

Soooo… how did people find their way down to the riverbank? I decided now was the time to find out. I kept an eye open for entry points while walking and – hardly a mystery – it turned out there were several openable gates that reveal steps leading down to the river. A few people were using the steps as extra seating and then – at river level – there were the Mudlarkers themselves. Instantly it felt like entering another world – one which was happily unfolding on its own terms independently of anything else going on at surface level. I saw five or six people there, each with their own Mudlarking motives. One elderly pair had collected a selection of (yellow) brick pebbles which they were juggling to carry while another woman washed off her find in a trickle of water coming from a Bankside outlet pipe. Further on. a man lay on his side, gently scraping away from a plateau of mud that rose from the surrounding shale. A huge wooden sign mounted on the river wall reads BANKSIDE, completely covered in dripping river greenery and criss-crossed with chains weighted with stones.

I made my way slowly through this new landscape, gazing no more than a few feet in front of me. Not sure what I was looking for. I’d read recently about someone regularly finding bullets and even a (live?) wartime grenade so I fixed on looking for some UXB ordnance. There were plenty of shattered pottery fragments amongst the pebbles, much of it clearly C18 and C19th, and some rough looking, mustardy glazed C17 candidates. Some have the occasional tantalising piece of text or image – unsolvable jigsaws. There were any amount of shattered clay pipe stems and bowls. Animal bones and teeth. It seemed bizarre that stuff so old, even rubbish, is all still here, churning for centuries, the uncurated museum of human detritus.

People in this shoreside realm seemed content to exist independently – people don’t come here to socialise. No-one challenged me or even seemed to notice I was there. After I’d covered 100 yards (in nearly 30 minutes) an older gentleman asked if I’d had any luck? Maybe my exceptionally slow shuffle suggested I was an expert. ‘Just browsing,’ I responded, nonsensically. I doubt my lovely yellow brick pebbles would have registered as significant finds with him.

Most of the things I collected on the short walk I threw back – I’d gathered them for the experience. A few I keep: the yellow brick pebbles and a small selection of tiles pieces and pipe sections, confident this haul would compare closely with those of most first-timers. But I felt thrilled with my finds, far more valuable than any of the tat on sale in the Tate Modern gift shop (where I was now emerging). The nature of the tides means there is new stock in twice a day and I feel certain I’ll return for further browsing the next time I manage to find the Thames.