The Mansi doctrine is a long-established planning principle which can be seen in action in an appeal case relating to the short-term letting of a basement flat in west London (DCS Number 400-024-249).
The enforcement notice required the use of the basement flat as short-term let accommodation to cease. The inspector agreed with the council that the use of the flat for short-term lets had a harmful effect on the borough’s housing stock and thereby conflicted with development plan policies. He recorded, however, that “The use of a residential property for temporary sleeping accommodation in Greater London constitutes a material change of use in certain circumstances, by virtue of the provisions of s.25 of the Greater London Council (General Powers) Act 1973. The Deregulation Act 2015 amended this provision to say that it does not apply in specified circumstances and where the use for temporary sleeping accommodation does not exceed 90 nights in a calendar year.” Accordingly, he pointed out that the notice would have the effect of prohibiting all temporary sleeping use. It is well-established law, he explained, that an enforcement notice should not preclude lawful uses (Mansi v Elstree RDC ). As the notice would have the effect of prohibiting use for temporary sleeping accommodation of no more than 90 nights, it would remove a lawful use and offend the Mansi doctrine. He therefore varied the notice to protect the lawful use provided by the Greater London Council (General Powers) Act 1973, as amended.
The details of the Mansi court case can be found at section 4.5362 of DCP Online.