Put the garlic, oil, parsley and lemon rind in a nonreactive bowl and toss in the prawns. Cover and leave to marinate in the refrigerator for at least 15 minutes and up to 1 hour.
Heat a ridged griddle pan over a high heat until smoking hot, or preheat a gas barbecue to high or, if using a charcoal barbecue, get the coals to the stage where there are no more flames and the coals are covered with a thin layer of grey ash.
Thread the prawns on to metal skewers and season with salt. Cook for 1–2 minutes on each side until the prawns have turned pink and are lightly charred. Serve immediately with lemon wedges.