Pat the mackerel completely dry inside and out with paper towels.

Using a sharp knife, cut three diagonal slashes through the skin on each side of the fish, cutting down to the bone.

Rub the fish all over with olive oil, then season with sea salt and black pepper, including inside the cavity.

Squeeze a little lemon juice over the outside of the fish and set aside while you prepare the sauce.

Place the gooseberries, water, and sugar in a small saucepan over medium heat.

Cook for 8-10 minutes, stirring occasionally, until the berries burst and collapse. Crush them lightly with the back of a spoon - leave it rough rather than smooth.

Stir in the butter and grated ginger, if using. Season with a pinch of salt.

Taste and add more sugar if the sauce is very sharp. Keep the sauce warm over very low heat while you grill the fish.

Preheat a cast-iron grill pan or outdoor grill over high heat for at least 5 minutes until very hot.

Place the mackerel on the grill and do not move them. Cook for 5-6 minutes until the skin is charred at the score marks and the fish releases cleanly from the grate.

Flip carefully using a fish spatula and cook for another 4-5 minutes on the second side until the flesh near the backbone is opaque and an instant-read thermometer reads 63 C / 145 F.

Transfer to a warm plate and rest for 2 minutes.

Spoon the warm gooseberry sauce alongside or over the mackerel.

Serve with lemon wedges and your choice of greens or new potatoes.