Scrub, scrape and halve the potatoes, then cook in salted boiling water for 8-10 minutes until tender.
Meanwhile, make the vinaigrette by mixing the olive oil with the vinegar, garlic oil and salt and pepper to taste, then mix in the dill. (To speed things up all the ingredients can be shaken vigorously in a clean screw top jar.)
Drain the potatoes and return them to their pan. Spoon over 2 tbsp of vinaigrette, cover the pan with its lid or a plate, and keep warm.
Gently warm the lactose free cream, lemon juice and dill for the cream dressing in another pan (a shallow one is best), stirring all the time until blended. Add the trout flakes and toss gently over a low heat until the fish is warm.
Scatter the salad and herb leaves over two plates, trickle over some of the remaining vinaigrette and spoon the dressed potatoes round the edge.
Gently stir the lemon zest into the fish, then spoon the fish and dressing into the centre of the salad. Serve straight away. Any leftover vinaigrette can be served separately or saved in a screw top jar in the fridge for up to a week.