Step 1 Butterfly prawns: slice along the back of each prawn to open it up. Place prawns, cut-side up, on a large baking tray. Drizzle with olive oil and scatter with garlic, ground coriander and half of the fresh coriander. Place prawns in fridge until required.
Step 2 Place tomato, onion, radish, cucumber, chilli, lime juice and remaining fresh coriander in a medium bowl. Combine well to make pico de gallo.
Step 3 Heat a barbecue or set a large grill pan over high heat. Grill prawns in 2 batches, turning once, for 3–4 minutes, or until just cooked through.
Step 4 Divide prawns among serving bowls or arrange on serving platter. Serve prawns with pico de gallo and lime wedges.