The owner of a house branded an eyesore by objectors is appealing against a ruling that may force its removal.
The Pembrokeshire Coast National Park refused retrospective planning consent for Bettws Newydd in Newport stating it was different from its original plans.
It also issued an enforcement notice for an alleged planning control breach which means it may be taken down.
An inquiry expected to last three days will hear from owner Nolan Nicholas and objectors to the building.
The row dates back to 2006 when planning consent was first granted for the site on an area of the coast known as the Parrog.
Once the house was build members of the park authority's development management committee ruled the structure was not what was originally approved.
They have since turned down two retrospective planning applications and issued the enforcement notice.
Mr Nicholas has appealed and a Welsh Assembly Government appointed planning inspector will hear from both sides during the hearing at Newport's Memorial Hall.
A decision is expected to be published later in the year.