Pat the oxtail dry with paper towels and remove as much visible fat as possible.
Place the oxtail in a stockpot and cover with plenty of cold water.
Cover with a lid and bring to the boil – turn the heat off and allow oxtail to stand for 20 minutes. Strain, discarding the water.
Place the oxtail on a clean plate and pat dry with paper towels.
Melt the oil in the stockpot and brown the oxtail on all sides. Remove and set aside.
Add the carrots, onion and celery and cook, stirring constantly, until lightly browned. Return the oxtail to the pot, along with the bouquet garni and bacon.
Add the stock – cover the oxtail completely. Bring to the boil slowly, skimming any excess fat from the surface. Cover with a lid and simmer over very low heat for 4 hours, checking that the oxtail is always covered with water.
When cooked, remove the oxtail to a chopping board.
Strain the stock in a large heatproof bowl and refrigerate overnight. Discard the contents of the strainer.
Remove the meat from the bones and shred. Refrigerate the meat overnight.
Remove the solidified fat from the surface of the soup and return the soup to the stockpot with the oxtail meat, extra carrot, onion and celery. Bring to the boil over medium heat and cook for 20 minutes.
Just before serving add the lemon juice, parsley and season with salt and pepper.