After 5 - 7 min, add the water, mustard, thyme, bay leaf, worstershire sauce and brown sugar. Once the water comes to a boil, cover and turn very, very low and allow to simmer at least 2 hours, adding a little water now and then if the liquid is much reduced, though this will be an indication it is on a little high.
After 2 hours add the remaining ingredients and allow these vegetables to cook very slowly (about 1 hour) until tender. Then stir in small amount of flour (1 Tbsp or so mixed in cold water) for thickening. If the gravy seems very pale, add an oxo cube or two, crumbled finely.
If possible, allow this to sit in the refrigerator overnight, (the flavour will be much improved) then heat just prior to serving (with crusty bread).