Without prejudice to the operation of section 90 of the M1Town and Country Planning Act 1990 (planning permission deemed to be granted in certain cases) in relation to any provision made by or under this Act or any other enactment which by virtue of this Act or the M2Water Act 1989 relates to the functions of a relevant undertaker, nothing in this Act or in any such enactment shall be construed as authorising the carrying out of any development (within the meaning of that Act of 1990) without the grant of such planning permission as may be required by that Act of 1990.