Cut fish into 1 inch cubes. wash pepper and deseed it. Cut into 1 inch pieces. To make marinade, mix olive oil, lemon juice, crushed clove of garlic and rosemary in a glass or china bowl. Do not use metal. Add salt and pepper. Put in fish, turning occasionally. Keep in marinade in fridge for 90 minutes to 2 hours. It can stay in the marinade for up to six hours, but not longer. When you're ready to cook kebabs, put fish on to skewers, not more than 3 or 4 cubes on each skewer, with pieces of pepper between each cube. Begin and end with pepper. Make sure all the pieces touch, but don't squash together. Push all up to sharp end, leaving a long handle to hold easily under grill or on barbecue. Line grill with foil saves washing up! and grill for 5 to 6 minutes a side. Do not put them too close to the heat they will burn on the outside before they are cooked inside these cubes are really meaty. They should take about 10 to 12 minutes to cook properly so they are succulent inside with wonderful borwn crispy bits on the outside. Serve with a rice pilau or even just crusty bread with some lemon juice to squeeze over them.