Provided always, That the Provisions of the said Lands Clauses Consolidation Act " with respect to the Purchase and taking of Lands otherwise than by Agreement" shall not be incorporated with this Act, save for enabling the Metropolitan Board of Works to take Land, or any Right or Easement in or over Land, for the Purpose of making any Sewers or Works for preventing the Sewage or any Part of the Sewage within the Metropolis from passing into the Thames in or near the Metropolis, or otherwise for the Purpose of the Sewerage or Drainage of the Metropolis: Provided also, that no Land, or Right or Easement in or over Land, for the Purposes aforesaid, shall be taken compulsorily by the said Board, without the previous Consent in Writing of One of Her Majesty's Principal Secretaries of State.