Jon Day.

We approach in darkness, in the chilled air of a winter morning. Billingsgate fish market keeps antisocial hours, opening at 5am and closing before 8.30. The squat, utilitarian building basks in the orange glow of sodium lamps and the 25,000 tonnes of fish that pass through here every year, now transported by road rather than river, have left their trace as an oily, mineral tang in the air. It’s noticeable rather than unpleasant; a smell that alerts you to the place’s purpose, an olfactory postcode. London used to be a city defined by its odours, but such specific and localised smells are rare in our age of scent sanitisation, and should be treasured.

The market has always existed alongside other institutions of exchange. For 900 years Old Billingsgate formed the frozen heart of the City of London, nestling alongside the banks and trading floors of the Square Mile. Originally a street market, in the nineteenth century the fishmongers were moved into a building designed by Horace Jones, next to the river on Lower Thames Street. For years the cries of porters and merchants, investing in cuttlefish futures, in gilt-head bream gilts, competed with those of the City’s other traders. The market clung to its riverside location until 1982, when it was exiled to its new site in Poplar, but it still shares space with the money-markets, lying at the feet of the thrusting towers of Canary Wharf. It left its mark on the architectural memory of the City: once vacated it took months for the cellars of Old Billingsgate to defrost, and there were fears that the building would collapse as the foundations thawed, depriving the structure of its scaffolding of ice. A faint fishy smell still hangs around Lower Thames Street.

A market constable nods to us as we enter through an enormous door, which opens and closes like a giant guillotine. It’s bright inside, the light reflecting off piles of glistening fish. Vast ice-machines line the walls, with men shovelling ice from them as though they were shovelling coals. White coated porters swirl around us, dragging ancient carts and bustling us out of the way with their cries of ‘mind your legs, mind your legs’. The space between the stalls is theirs, and they don’t think much of those of us who aren’t buying by the barrel, who don’t need their services. Though they don’t wear the leather archer’s hats they used to, their white smocks are still made of sailcloth, an old yet practical uniform. In one corner of the market a group of trainees learn the price of fish.

The stars of the show, lying on their beds of ice, are the fish: salmon the size of a man’s leg, velvet-skinned tuna plump like pin cushions, crabs and lobsters doing battle in polystyrene boxes, baskets overflowing with brilliant green samphire grass, endless chevroned mackerel, scallops coyly displaying their orange corrals, huge piles of crenulated oysters. There are strange, alien creatures also: the cutlass fish, a metre-long ribbon of mirror, the smooth-faced mahi-mahi, with its massive forehead and eyes like a mooncalf’s, the bloated and poisonous fugu.

The fish are cheap, but you have to buy in bulk. We stagger out into the breaking dawn, weighed down by a box of oysters, a brace of crabs, and many kilos of prawns. Back home, still slightly dazed, a breakfast of oysters and crab newburg on toast, then back to bed.