To cook the haddock: Lightly dust both sides of the fish with the seasoned flour. Heat a little oil and a small knob of the butter in a large heavy-based frying pan over a medium heat. When hot, add 2 of the haddock fillets to the pan, skin-side down. Fry for 2-3 minutes until lightly golden and crisp. Carefully turn the fillets over and cook for 2-3 minutes on the other side until they are golden and crispy. Set aside and keep warm while you cook the rest of the haddock fillets. Keep the fish warm while you make the sauce.
To make the sauce: Heat the remaining butter in the pan until it starts to smell nutty, then add the capers and squeeze in the juice from one of the lemon halves. Stir, then spoon the lemony caper butter over the fish to serve. Sprinkle on the parsley and serve with the remaining lemon half, cut into wedges, for squeezing.
Delicious with new potatoes and steamed purple sprouting broccoli.