1. Start by preparing the BBQ: use firelighters and charcoal, letting the coals become white-hot and evenly distributed.
2. To make the sauce, heat olive oil in a pan. Add grated garlic and finely sliced chillies, frying gently for about 2 minutes until the garlic turns light golden brown. Add lemon zest and juice, and cook gently, ensuring the garlic does not burn.
3. Pour half of the olive oil and garlic mixture over the cleaned prawns, massaging the marinade under the shells for an even coating.
4. Place prawns on a hot grill, cooking each side for about 45 seconds to 1 minute until the shells are pinky-orange and meat is pearl white. Control flames to avoid burning; sprinkle water if necessary.
5. Remove prawns from heat, place them on a clean tray, and drizzle with the remaining sauce. Serve immediately with fresh lemon wedges and crusty bread or rice to soak up the sauce.