For the vinaigrette: add the mustard and vinegar to a clean jar. Now add the oil and season with salt and pepper. Shake well.
In a large saucepan add the haricot beans, thyme, carrot, bay leaf and onion. Cover completely with cold water. Do not add salt at this stage. Bring slowly to the boil and then turn down to a simmer. Cook for about 40 minutes or according to packet instructions. Season very well with salt and pepper and drain off cooking liquid. Place in a large salad bowl.
In a pan fry the pancetta until crispy, drain off fat and add to the beans. Add remaining ingredients and dress with the vinaigrette.