Rinse the lentils, then drain, place in a saucepan and cover with twice their volume of boiling water. Simmer for 15 minutes, or until just tender.
Meanwhile, season the fish fillets, then halve each slice of Parma ham and roughly wrap around each fillet. Heat a frying pan, add 1 tablespoon of the oil and cook the fish for 2 minutes until lightly browned on the underside. Drizzle another tablespoon of the oil over the fish. Place the pan under a preheated hot grill, making sure you turn the handle away from the heat if not flameproof, and cook for 5–7 minutes until just cooked through. Mix together the remaining oil, vinegar and garlic.
Cool the lentils a little under the cold tap, then drain. Toss through the spring onions, spinach and tomatoes, then stir through the dressing. Serve alongside the fish.