Mix lemon juice, garlic and oil together. Peel potatoes and cut into walnut sized pieces. Put into a casserole dish and pour the lemon juice/oil mixture onto the spuds. Sprinkle the thyme on then pour water into the dish so that it comes just over halfway up the sides of the potatoes. Sprinkle on salt and pepper. Bake at 400F/205C for about an hour or at 350F/180C for about an hour and a half. Turn the potatoes in the middle of the cooking time. The liquid will be mostly absorbed into the spuds when they're done.