Cook bacon until crisp in a 3 litre saucepan. Remove from pan. Add olive oil, onion, carrot, celery. Saute until onion is soft but not brown. Stir in stock, potatoes and cayenne. Bring to the boil, reduce heat and simmer until potato is tender. Stir in cheese until just melted - do not boil. Add bacon, season to your taste and serve!