Lay the bacon slices in a single layer in a large frying pan. Fry over medium heat until it begins to get tinged with brown. Fry on both sides. Remove from pan, but save dripping.
Melt butter in frying pan. Crack eggs into pan, being careful not to break yolks. Place tomato slices, mushrooms and bread in pan. Fry gently, stirring mushrooms and tomatoes occasionally. Keep everything separate. Turn bread over to brown on both sides.
When egg whites are set, but yolks are still runny, dish half of everything onto each of 2 warmed plates, and serve immediately.