Preheat grill to medium. Place all ingredients in a large bowl and mix together well.

Using your hands, shape mixture into 8 round flat burgers, each about 1cm (1/2in) thick. Place on rack in grill pan; grill for about 20 minutes until burgers are cooked to your liking, turning once or twice. (Don’t grill burgers too close to the heat – position about 8cm/3 1/4in from heat.) Serve in baps with salad and relish.