A closure notice, an extension notice, a cancellation notice or a variation notice must be served by—
The constable or local authority representative must if possible—
If the constable or local authority representative reasonably believes, at the time of serving the notice, that there are persons occupying another part of the building or other structure in which the premises are situated whose access to that part will be impeded if a closure order is made under section 80, the constable or representative must also if possible serve the notice on those persons.
The constable or local authority representative may enter any premises, using reasonable force if necessary, for the purposes of complying with subsection (2)(a).
In this section "representative", in relation to a local authority, means—