Heat the oil in a small non stick frying pan approximately 20cm diameter and fry the bacon for 2 minutes. Add the mushrooms and fry for 3 minutes then stir in the potatoes.
Whisk the eggs and milk together, season and pour into the frying pan. Cook gently for 3 to 4 minutes loosening the edges with a spatula. Place under a preheated grill for 2 to 3 minutes, adding the tomatoes for the last 1 minute, until golden and cooked throughout.
Cool slightly before turning out of the frying pan.