A number of defences have been pleaded in an action for nuisance. Some of the defences have been recognised by the courts as valid defences and some others have been rejected. There are many valid defences available to an action for tort. Effectual Defences 1. Prescriptive right to commit nuisance A right to do an act, which would otherwise be a nuisance, may be acquired by prescription. Example- If a person has continued with an activity on the land of another person for 20 years or more, he acquires a legal right by prescription, to continue therewith in future also. On the expiration of this period of 20 years, the nuisance becomes legalised ab initio as if it has been authorized by a grant of the owner of servant land from the beginning. In the case of, Sturges v/s. Bridgman ,the defendant, a confectioner had a kitchen in the rear of his house. For over twenty years, confectionery materials were pounded in his kitchen by the use of large pestles and mortars, and the