Use one unpeeled potato per person. Cut into 8 pieces. Put into cold salted water & bring to boil- cook for 5-10 minutes Drain & let dry a bit.
Meanwhile, preheat oven to 200 celsius.
Slice aubergine & cut into quarters (not too thin!). Mix with potatoes on baking sheet, spray about 40 times with low calorie cooking spray (only 40 cals so dont worry). If you are not on a diet, use olive oil. Put sheet into middle of oven.
Cut red pepper up into chunky pieces.
Put cod (fillet or loin, whatever) into baking tin/tray (not too shallow, a loaf tin is ideal). Squeeze over juice of half a lemon, add salt and chopped (or dried) oregano & parsley. Cover tray in foil. After potatoes have been in for 15 mins, put the fish inches At same time, add peppers to the potatoes, give another mix & add more oil/ spray if necessary. This will need to cook for 30 mins more.
Make sauce- bit of oil/spray in saucepan, add chopped onion & garlic, cook for a bit. Add mushrooms. Reduce. Add sliced olives & can chopped tomatoes. Done.
Pour sauce over fish or serve on side.