Cut the rind off the bacon. Put both in a pot and cover with 1 1/2 litres of water. Bring to the boil and simmer for about 45 minutes
Wash the lenses. Add the lentils and bay leaf to the bacon and bring to the boil. Cook for another 45 minutes. Peel, wash and chop carrots, celery and potatoes. Add to the lentils after about 15 minutes. Clean, wash and chop the leek
About 15 minutes before the end of the cooking time, remove the bacon and cut into cubes. Cut mettenden into pieces. Add the ends of the mead, bacon and leek to the soup. Season with marjoram, salt, pepper, vinegar, mustard and sugar. Remove bacon rind. Serve the soup