18Service of documents.
All documents required to be served on the Crown for the purpose of or in connection with any civil proceedings by or against the Crown shall, if those proceedings are by or against an authorised Government department, be served on the solicitor, if any, for that department, or the person, if any, acting for the purposes of. this Act as solicitor for that department, or if there is no such solicitor and no person so acting, or if the proceedings are brought by or against the Attorney General, on the Solicitor for the affairs of His Majesty's Treasury.