Paragraph 40 I1

The fact that any act or thing may have been done by the drainage authority on behalf of the undertaker or in accordance with a plan approved or deemed to have been approved by the drainage authority or in accordance with any requirement of the drainage authority or under its supervision does not, subject to paragraph 39, excuse the undertaker from liability under the provisions of sub-paragraph 38(1) unless the drainage authority fails to carry out and execute the works properly with due care and attention and in a skilful and professional like manner or in a manner that does not accord with the approved plan.