If unauthorised works are being undertaken to a listed building, a local planning authority may issue a temporary stop notice to require the immediate cessation of specified works for a period of 28 days. If an agreed resolution to the situation cannot be reached within that time, an enforcement notice may be used to require the restoration of the building to its former state or, if that is not practical or desirable, to specify measures to alleviate the effect of the unauthorised works. An enforcement notice may also be used to specify further works needed to carry the terms and conditions of a listed building consent into effect.
It is an offence to carry out any works to a listed building that would affect its character as a building of special architectural or historic interest without appropriate listed building consent; to fail to comply with a condition attached to a consent; or to perform or permit an act with the intention of damaging a listed building. Failure to comply with either a temporary stop notice or an enforcement notice constitutes an offence in addition to any arising from the unauthorised works.
In the event of a prosecution for unauthorised works, the accused may offer as a defence that the works were urgently necessary in the interests of health and safety or the preservation of the building. For such a defence to succeed, the works must have been limited to those immediately necessary and as soon as reasonably practicable written notification justifying the works must have been given to the local planning authority.
In most instances, a person found guilty of one of the offences mentioned above will be liable to a fine. However, a term of imprisonment may also be imposed on conviction for unauthorised works.