Method
Take the fish out of the fridge about an hour before cooking so they are not cold in the middle.
Light your fire or barbecue and allow it to burn down to a steady bed of glowing embers. You want a moderate heat rather than fierce flames, so the fish can cook through gently without burning.
Make sure the grill is clean. Give it a good scrub with a wire brush, then oil it lightly. Set the grill over the fire and allow it to heat well before adding the fish.
Rub the fish all over with the olive oil and season generously with salt and pepper.
Place the fish dark skin side down on the hot grill. Let them cook undisturbed for about 4 to 5 minutes. Carefully ease a corner up with a spatula to check the underside. The skin should be lightly charred and releasing easily from the grill.
Continue cooking for another 3 to 4 minutes, then carefully turn the fish using two spatulas. Scatter the chopped garlic and parsley over the crisp hot skin straight away so it hits the heat and begins to sizzle. Squeeze over the juice of half the lemon.
Cook the fish for a further 3 to 4 minutes until the flesh at the thickest part flakes easily away from the bone.
Lift the fish from the grill and transfer to a board or platter. Serve straight away with the remaining lemon cut into wedges.