Rub the fish with salt and pepper, then lightly rub with olive oil. Stuff each cavity with the lemon and some of the elderflower. Tie the fish at regular intervals with kitchen string.
Make the tomato salad. Arrange all the tomatoes in a shallow bowl. Season and drizzle over the olive oil and vinegar. Leave for 10 minutes, then sprinkle with the chopped herbs.
Preheat a charcoal