Place the potatoes in a large pan of boiling salted water and cook for 20 minutes or until tender. Drain well and tip onto a large roasting tray.
Preheat the oven to 220C/200C Fan/Gas Mark 7.
Toss the onion, courgettes, peppers, olive oil and tomatoes with the juice of 1 lemon in the roasting tray along with the boiled potatoes.
Wrap each monkfish with a slice of Parma ham, then lay it on top, over the rest of the vegetables and garlic and drizzle with 15ml lemon juice. Season well, then cover with foil.
Roast in the oven for about 30-35 minutes until just tender and cooked through (add a little more cooking time if the fish is very thick at the tail end).
Squeeze over 1 more lemon to taste before serving, along with some fresh basil leaves.
Serving Suggestions: Serve immediately with fresh bread to mop up any juices.