Cut the turkey breasts into 1 in (25 mm) cubes. Heat the olive oil in a large casserole dish. Add the turkey pieces and cook over a moderate heat for 5 minutes, stirring continually, until lightly browned.

Remove the turkey with a slotted spoon, leaving the oil in the dish, and put to one side.

Thinly slice the onion, carrots, swede, turnips, celery and leek. Add them to the oil remaining in the dish and cook for 2 - 3 minutes, turning continually.

Return the turkey to the dish and stir in the flour. Add the canned tomatoes, stock and herbs. Season lightly to taste and bring to the boil.

Scrub and peel the potatoes, then thinly slice them. Remove the dish from the heat and arrange the potato slices to cover the top of the turkey and vegetables, starting from the outside and working inwards, overlapping in concentric circles. Dot the potatoes with little bits of butter.

Cover the dish with a lid, or with foil wrapped tightly over it, and cook in the preheated Oven for about l 3/4 hours, then uncover and cook for a further 45 minutes until the potatoes are really crisp and golden. Serve immediately.