26. Prior to the commencement of the authorised development, excluding earthworks, archaeology works or ecological mitigation works, a foul water drainage strategy must be submitted to and approved in writing by the relevant planning authority. Except where it is constructed in accordance with the approved foul water drainage strategy, no phase of the authorised development is to commence until written details of the foul water drainage system have been submitted to and approved in writing by the relevant planning authority. Such details must be implemented as approved from time to time by the relevant planning authority.