Heat the oven to 200 C / 390 F. Toss the potato slices in a 30 cm / 12-inch mixing bowl with 2 tbsp olive oil, 1 tsp salt, half the pepper, the lemon zest and the leaves from 2 thyme sprigs.

Spread the potatoes on a rimmed 33 x 46 cm / 13 x 18 inch sheet pan in a slightly overlapping layer. Roast for 20 minutes, stirring once at the 10-minute mark, until the edges just start to color.

While the potatoes roast, rinse the dentex inside and out and pat it very dry with paper towels. Cut three shallow slashes into each side, then season the skin and cavity with 1 tsp salt and the remaining pepper.

Fill the cavity with the 3 lemon slices, 2 garlic cloves, the parsley stems and the remaining 2 thyme sprigs. Rub the whole fish with 1 tbsp olive oil.

Pull the pan from the oven. Scatter the tomatoes, olives and the last garlic clove over the potatoes, then lay the fish on top, diagonally if needed. Pour the wine into the potatoes beside the fish and drizzle the remaining 1 tbsp oil over the vegetables.

Bake for 30 minutes, checking at 25, until the skin is lightly golden, the flesh near the backbone is opaque and a thermometer in the thickest part reads 145 F / 63 C.

Rest the fish on the tray for 5 minutes. Squeeze the lemon juice over the top and scatter the chopped parsley leaves. To serve, run a knife along the backbone, lift off the top fillet, remove the bone, then lift out the bottom fillet and spoon the potatoes and juices alongside.