Section 57(7).
1E+WWhere on lst July 1948 land was being temporarily used for a purpose other than the purpose for which it was normally used, planning permission is not required for the resumption of the use of the land for the latter purpose before 6th December 1968.
2E+WWhere on 1st July 1948 land was normally used for one purpose and was also used on occasions, whether at regular intervals or not, for another purpose, planning permission is not required in respect of the use of the land for that other purpose on similar occasions on or after 6th December 1968 if the land has been used for that other purpose on at least one similar occasion since 1st July 1948 and before the beginning of 1968.
3E+WWhere land was unoccupied on 1st July 1948, but had before that date been occupied at some time on or after 7th January 1937, planning permission is not required in respect of any use of the land begun before 6th December 1968 for the purpose for which the land was last used before 1st July 1948.
4E+WNotwithstanding anything in paragraphs 1 to 3, the use of land as a caravan site shall not, by virtue of any of those paragraphs, be treated as a use for which planning permission is not required, unless the land was so used on one occasion at least during the period of two years ending with 9th March 1960.