Set the lentils to soak in some cold water while you prepare the other ingredients.
Peel and chop the carrots and swede.
Wash and shred the cabbage
Dice the onions,
Add the onions, carrots, swede and cabbage to a large saucepan, together with the chopped tomatoes and stock.
DO NOT add any salt at this stage.
Bring the ingredients to a boil and then reduce to a simmer until all the vegetables are softened. This should be around 25 - 30 minutes.
Drain the lentils in a sieve and then run them under the cold tap to wash away as much dust as possible.
Add the lentils to the saucepan and continue cooking until the lentils are soft, making sure you stir the saucepan every few minutes to prevent the lentils from burning.
The cooking time for the lentils should be around 10-15 minutes but check the pack for guidelines.
Once cooked, remove from the heat and allow to cool for a few minutes before blending with an immersion blender to your desired consistency.
Taste and season with salt and pepper as desired.
If using leftover gammon, cut the meat into small diced pieces and add to the soup,
Serve with your favourite bread.