The local planning authority may issue a notice (an "enforcement warning notice") where it appears to them that—
there has been a breach of planning control in respect of any land in England, and
there is a reasonable prospect that, if an application for planning permission in respect of the development concerned were made, planning permission would be granted.
The notice must—
state the matters that appear to the authority to constitute the breach of planning control, and
state that, unless an application for planning permission is made within a period specified in the notice, further enforcement action may be taken.
A copy of the notice must be served—
on the owner and the occupier of the land to which it relates, and
on any other person having an interest in the land, being an interest that, in the opinion of the authority, would be materially affected by the taking of any further enforcement action.
The issue of an enforcement warning notice does not affect any other power exercisable in respect of any breach of planning control.