Thoroughly defrost your prawns. Using kitchen scissors and starting just behind the head, snip along top of tails, reaching a quarter inch into the flesh. Remove 'vein' and any gunk just behind the head. Rinse well.
Dry them, then rub oil all over.
Press the prawns into a sprinkling of salt. Make sure the salt adheres, especially into the snip (but don't over do it).
The grill or BBQ should be very hot. Put the prawns on or under the heat. Cook for about 5 minutes, turning after 3.
Serve with lemon quarters and a salad. Diners should apply the lemon after peeling the prawns.