Why British oysters are worth the fuss

The first time you order a native oyster, you may wonder what all the ceremony is about. A rough grey shell, a wobble of brine, a squeeze of lemon. Then you taste it — a rush of cold sea, a mineral tang, a sweetness that lingers longer than you expected — and the fuss starts to make sense.

Britain has eaten oysters for thousands of years. Roman middens along the Thames are packed with shells, and for centuries they were ordinary food, sold from street stalls and stirred into pies. Our native beds later collapsed through overfishing, pollution and disease, and what remains is precious. These days, choosing a native is not just a nice lunch. It is a small act of support for a battered, recovering fishery.

Native versus rock: what's the difference?

Almost everyone starts with rock oysters, and that is no bad thing. They are milder, firmer and more forgiving, which makes them the sensible gateway oyster. But natives are the ones worth learning to love.

• Native (Ostrea edulis) — round, fairly flat on top with a genuinely deep bottom shell that holds a generous pool of liquor. The flavour is rich, complex and long: think copper, cucumber skin, hazelnut, sometimes a faint metallic edge. They grow slowly, taking three to five years to reach the plate.
• Rock (Crassostrea gigas) — longer, craggier and more irregular, with a frilly, fluted exterior. They grow quickly, mature in around eighteen months and taste milder, brinier and creamier, with melon and seaweed notes. Far more of them about, and far cheaper.

If you are new to raw shellfish, order a couple of each side by side. The contrast will teach you more in one sitting than any tasting note can.

Where in Britain they come from

Native oysters are a creature of sheltered, silty estuaries and sea lochs, and the map of British oyster country follows those waters. The Essex estuaries around Mersea and the Blackwater are the classic native grounds, still worked in winter by dredgers under sail. Kent has Whitstable, Seasalter and the Swale, where the native fishery is woven into the town's identity. In Scotland, Loch Ryan is famous for natives, while the west coast sea lochs produce excellent rock oysters. Northern Ireland's Lough Foyle and Carlingford Lough have long native traditions, and Cornwall, Devon, Wales and the Menai Strait supply most of our rock oysters.

Ask where your oysters were grown. Any good fishmonger will know, and the answer usually explains the flavour.

Buying and storing them properly

Buy from a reputable fishmonger or a classified harvesting area — never pick your own from a random shore, as water quality varies enormously and shellfish concentrate whatever is in it.

• Check the shells. They should be tightly closed. Tap any gaping one sharply; if it will not shut, it is dead. Discard it.
• Use your nose. Fresh oysters smell of clean, cold sea. Anything sour or ammonia-like is past it.
• Keep the tag. The label gives the harvest area and date, which is useful if anything goes wrong.
• Store them right. In the fridge, cup-side down so the liquor stays put, under a damp tea towel. Never in fresh water, never sealed in a plastic bag, and not buried directly in ice.
• Eat them quickly. Within two or three days, ideally. Natives in particular do not sit around well.

Opening and eating: the practical bit

You need an oyster knife — short, stiff blade, no give — and a folded tea towel to protect your hand. Hold the oyster cup-side down, hinge towards you. Work the tip into the hinge, twist to lever the top shell up, then slide the blade flat along the inside to cut the muscle. Keep the shell level so you do not lose the liquor, which is most of the point.

Then chew. Two or three chews, not one gulp — that is where the flavour opens up. Serve them cool rather than ice-cold, since freezing numbs everything good about them. A squeeze of lemon, cracked black pepper or a shallot vinegar is plenty; a dash of hot sauce is fine if that is your habit. To drink, a dry white, a crisp cider or a stout all work well.

One note of caution: raw shellfish carries a small risk, so if you are pregnant, immunocompromised or otherwise vulnerable, choose cooked oysters instead.

Seasons, size and the R rule

The old rule about only eating oysters in months containing an R exists for a reason. Natives spawn in summer, when the flesh turns milky and thin, so the traditional season runs from September to April. Rock oysters are grown to stay firm year-round, which is why you can order them in July.

Natives are usually sold by grade or weight, while rock oysters are often numbered, with three being the common sweet spot and larger numbers meaning smaller oysters. Whatever you buy, look for well-managed fisheries and native bed restoration work, and pay the extra for natives when you can. They are slower, rarer and more interesting — and every one you eat helps keep the tradition alive.