Heat the oven to 350°F Tip the duck legs into a large bowl and season with salt and pepper. Scatter over the flour and toss the duck legs until coated. Heat the oil in a large casserole dish / dutch oven with a lid and spend a good 10 mins slowly browning the duck on all sides - try to get as much color on it as possible.
Remove the duck to a plate and add the carrots, onion and garlic to the pot and cook for 5 mins until just beginning to color.
Nestle the duck legs amonst the vegetables and pour over the wine. Add the herbs, season then bring everything up to the boil. Cover with a lid and place in the oven, undisturbed for 1 1/2 hours.
Remove from the oven and leave to cool. Lift the duck into a container, strain the sauce into another and chill both for at least 2 hours or up to 2 days. At this point the duck can be frozen for up to 3 months.
Once chilled, lift the fat off the sauce and set aside for roasting potatoes inches Heat a large saucepan and sizzle the bacon for 5 minutes Turn up the heat and add the mushrooms. Cook for 3-4mins.
Return the duck and sauce to the pan and simmer for 10 mins until the duck is heated through and the sauce has reduced a little.
Serve each person a duck leg with some sauce poured over along with green beans and potatoes roasted in the duck fat, if you like.