Peel the potatoes, carrots and onions then roughly chop the carrots, onions and celery. Slice the potatoes thinly and place these in a bowl of cold water. Trim all visible fat from the lamb and cut into bite-sized pieces
Arrange all the meat and veg (apart from the potatoes) in a large casserole making sure everything is evenly distributed.
Sprinkle the chopped thyme over the top and season well with salt & pepper
Make up the lamb stock and stir in the tomato puree and Worcestershire sauce. Pour over the meat and veg.
Arrange the sliced potatoes on the top so they overlap, season again and then spray with frylite.
Cover with tinfoil and bake for an hour.
Remove the tinfoil, spray again with drylite and continue to bake for another 20 minutes or until the potatoes are crispy and everything is cooked through. Serve with plenty of steamed vegetables