Material change of use Q & A DCP Section 4.32
The so called "second leg" of the definition of what activities require planning permission, as set out at sec.55 of the 1990 Act, states that "the making of any material change in the use of any buildings or other land" is development. However, due to the huge variety and subtlety of uses that may be made of land and buildings, this concept has created far more difficulty in interpretation than its operational development counterpart, already described at (4.31).