Juice one orange and half of the lemon. Cut and remove the rind from the remaining orange and lemon half then slice.
Place the fish fillets in a shallow dish in one layer and drizzle over 4 tablespoons of the olive oil and half of the pepper.
Lay the orange and lemon slices on top. Cover the dish and refrigerate for 4 hours.
Finely slice the basil leaves in a chiffonade.
Mix the flour with the salt and remaining pepper. Pat the fish dry with paper towel and dip in the flour. Shake off any excess.
Heat the remaining oil in a large pan over a medium to high heat.
Place the fish skin down in the pan and leave to cook for 2 minutes.
Turn over carefully and cook the other side for a further 2 minutes.
Remove the fish and keep warm while you make the sauce.
Add the butter to the pan to melt then stir in the lemon and orange juices for a minute.
Stir in the basil then pour over the fish.
Garnish with the marinade fruit slices to serve.