In a pan boil the potatoes until tender. When cool peel and slice thinly.

Heat the extra virgin olive oil in a pan and fry the onion and garlic until soft and golden but not brown.

Meanwhile preheat the oven to Gas Mark 5/190C. Brush a 2 litre capacity ovenproof dish with extra virgin olive oil and layer the base with sliced potatoes. Sprinkle over half the onions.

Place the fish on top and sprinkle over the herbs. Add a layer of sliced tomatoes and then another layer each of potatoes and onions. In a measuring jug whisk together the lemon juice, white wine and saffron mixture and pour over the potatoes.

Season with salt and freshly ground pepper and drizzle over extra virgin olive oil. Bake in a preheated oven for 30 minutes until the potatoes are crispy and the fish is cooked. Serve at once with boiled spinach.