- Place the cranberry juice, raspberries and peach slices in a small saucepan, bring to the boil then reduce the heat and simmer, uncovered, for 10 to 15 minutes or until mixture is reduced by about half.
- Allow to cool slightly then transfer to a blender or food processor and process or blend until smooth. Strain through a sieve, discarding the solids.
- Whisk the olive and walnut oils, lemon juice, salt and white pepper into the pureed fruit. Allow the sauce to stand at room temperature whilst you cook the fish.
- Preheat the grill to hot. Brush the fish with olive oil and place in a foil-lined grill pan. Grill for 10-15 minutes, turning once, or until the fish is cooked.
- To serve - Transfer the fillets to a warmed serving platter, drizzle with a little of the fruit sauce, transfer the remaining sauce to a sauceboat to pass round.