Roast the duck with the chopped onions and carrots.
Remove the roast duck taking care to remove as much fat as possible. Add the white wine, water, tomato puree, bouquet garni, salt and pepper. Allow to simmer gently for up to one hour. Strain and put to one side.
Caramalise the sugar and mix in the vinegar and then the strained liquids.
Melt the butter in a pan and add the flour and fry for 5 minutes. Slowly add the liquids to the butter and flour stiring continuously over the heat until a smooth sauce is produced. Add the grated rind and juice of the oranges and the half lemon. Simmer until thick and then add the Grand Marnier. Pour over the duck and decorate with slices of orange.
You can return the duck to the oven if you wish to crispen the skin or serve immediately.