Arrange the peppers, skin sides up, in the base of a grill pan then add the aubergines and courgettes in a single layer. Drizzle with 3 tablespoons of the oil, sprinkle with the garlic and season well. Cook under a preheated grill for 10 minutes, turning once. Set aside the courgettes and grill the peppers and aubergine for 5 more minutes until softened and the pepper skins charred. Wrap the peppers in foil and allow to cool.
Cut a slice off the top of the loaf then scoop out the centre to leave a case about 2 cm (¾ inch) thick. (Make the soft bread centre into breadcrumbs, stuffing or bread pudding.) Mix the remaining oil with the pesto, season and spoon or brush over the insides of the loaf.
Skin the peppers then arrange the orange peppers in the base of the loaf, cover with pastrami or ham, then the courgettes. Add the mozzarella slices, the red peppers and finally the aubergine slices along with any of the cooking juices. Replace the lid of the loaf, wrap in greaseproof paper or foil and keep in a cool place until required. When ready to serve, cut into thick wedges and serve with salad. Ideal for al fresco dining or a picnic.