A listed authority shall within the period of three years beginning with the date when a Scheme or a revised Scheme is prepared and published for the purposes of articles 2 or 4 put into effect the actions identified for the purposes of article 2(6)(a), (b) and (e).

Nothing in this article imposes any requirement on a listed authority where, in all the circumstances, it would be unreasonable or impracticable for it to perform the requirement.