Heat the oil in a non-stick wide, shallow pan, add bacon and fry briskly until lightly coloured, then lift on to a plate. Add the chicken and fry on each side until lightly brown. Set aside with the bacon. Tip onion and garlic into the pan and cook for 5 minutes. Stir in the flour and tomato purée, then stir over a low heat for 2-3 minutes. Add the wine, stock, lentils and thyme. Bring to the boil, reduce the heat, cover and simmer for 5 minutes.
Stir in the mushrooms. Add the bacon and chicken, pushing them under the liquid. Cover and simmer for 20-25 minutes, or until lentils are tender and the chicken cooked. Season with salt and pepper.