In 1991 the law on enforcement was reformed by the Planning and Compensation Act . The 1991 Act provided for a new 10 year limitation period. Thus, Town and Country Planning Act 1990 s171B now states that in the case of breaches of planning control "no enforcement action may be taken after the end of the period of 10 years beginning with the date of the breach". For changes of use to a single dwelling house this period is four years. Since the 1991 reforms the generally held view of planning lawyers is that the use need not be continuous, and the breach of planning control is the actual change. Discusses "Thurrock v SoS for Environment", which appears to signal a significant change in the law. The judge held that the use had to be continuous throughout the ten years in order to be immune from enforcement action. Thus, this ruling means that in future it will not be sufficient for appellants and applicants for lawful use certificates to show that the material change of use occurred over 10 years ago. They will now have to demonstrate that it has been continuous since that time.