Trim stem ends of peppers, and scoop out seeds and fibres.
Trim crusts from bread; soak bread in milk until thoroughly moistened; drain. Mix together with beaten egg and chopped tomatoes and olives. Drain tuna fish; flake it, and add to stuffing mixture. Mix well, and season to taste with salt and freshly ground black pepper.
Stuff peppers with mixture and place in a heatproof b