Preheat the oven to 200°C, 400°F, Gas Mark 6.
Tear the bread into small pieces, put into a food processor or grinder and pulse until you have fine crumbs. Spread the breadcrumbs out on a non-stick baking tray and toast in the oven for 10 minutes, then remove to a bowl and mix in the lemon zest.
Meanwhile, place the beaten egg in a shallow dish. Season the fish on both sides then dip into the egg and then the breadcrumbs and place on the baking tray.
Cut the potatoes into thin chips and place in a saucepan. Add the stock cube and just cover with water. Bring to the boil and cook for 5 minutes.
Drain well and place on a separate non-stick baking tray. Spray lightly with oil and cook in the oven along with the fish for 15 - 20 minutes until golden brown.
Combine all the sauce ingredients in a bowl. Serve the fish with the tartare sauce, chips and 100g garden peas per person.