Choose a new cookbook worth up to £28 when you subscribe to our magazine.
Heat oven to 200C/180C fan/gas 6. Place the potatoes in a pan of water and boil for 10-12 mins until tender. Add the beans for the final 2-3 mins. Drain well and slice the potatoes in half. Tip into a roomy baking dish and toss with the olives, lemon zest and oil. Season well.
Season the fish and wrap with the pancetta or bacon. Place on top of the potatoes. Bake for 10-12 mins until cooked through, then add a squeeze of lemon juice and scatter with tarragon before serving.