Start making the beans. Heat 3 tablespoons of the oil in a large shallow casserole, sauté pan or deep frying pan with a lid and fry the onions and celery gently for 10 minutes, or until softened and beginning to brown, stirring regularly. Add the garlic and cook for 3 minutes or more, stirring frequently.
Pour the rest of the oil into the pan and add the paprika. Cook for a minute, stirring constantly. Next add the tomatoes, passata and the beans with all their liquid. Season with lots of pepper; you shouldn't need extra salt as the beany liquid will already be fairly salty. Bring to a gentle simmer and cook for 10 minutes, stirring regularly.
Meanwhile, place a nonstick frying pan over a medium-high heat, add the 1½ tablespoons oil and then the fish, skin-side down. Season with salt and pepper and cook for 2 minutes. carefully flip the fish over, add a dash more oil and cook for a further 4 minutes, or until pale golden and almost cooked through.
Lift the fish gently on to the cooked beans, cover the pan with a lid and simmer gently for a further 4-5 minutes, or until the fish is just cooked: it should be firm but ready to flake into large pieces if prodded. Take off the heat, drizzle with a little extra virgin olive oil, squeeze over the lemon juice and scatter lots of chopped parsley on top. Serve with crusty bread.
