Toss the aubergine, courgettes, peppers and garlic with the olive oil and place in a large roasting tin. Bake in a preheated oven, 220°C (425°F), Gas Mark 7, for 50 minutes. Remove the tin from the oven and stir in the tomatoes, adding a little extra oil if necessary.
Whisk together the oil, vinegar, sugar and a little seasoning. Stir 3 tablespoons of the dressing into the vegetables and leave to cool.
Place the bread in a bowl. Add the measured boiling water to the remaining dressing and stir into the bread, then leave to soak for 10 minutes.
Add the bread to the vegetables with the basil and season to taste before serving.