Royal Mail has said it has no choice but to deliver post to a caravan sited illegally on land behind Panmurefield Village outside Dundee.
The caravan was moved on to the site on North Balmossie Street, between Panmurefield Village and Wyvis Road, in September.
Since then the owners of the caravan have erected steel fencing around the caravan so nobody can see in.
They have now also installed CCTV cameras in the trees above the caravan and even a mailbox.
Planning permission was sought to build a house on the site in January but refused by Dundee City Council.
As the land is at the top of a steep slope, the house would have been propped up on stilts.
It appears the caravan is also being propped up by paving slabs.
Although the land is understood to be privately owned, no permission has been granted for a caravan to be on the site.
Permission for the house was refused by the council because of concerns over its impact on the environment and the privacy of nearby properties and a lack of parking spaces.
However, the caravan’s occupants are now secure enough to have set up a postbox on the fence outside the caravan.
A Royal Mail spokeswoman said: “If we get mail for an address then we have to deliver it.”
A woman in the compound refused to speak to The Courier when approached last week.
Although the caravan has been set up illegally, she threatened to call the police when approached by a reporter.
She said: “That’s all we need. If you don’t go, I’m calling the police.”
She declined to comment further.
Dundee City Council launched an investigation following the appearance of the caravan in September.
A Dundee City Council spokeswoman said: “We are aware of the situation and an investigation is taking place.
“We will respond to findings appropriately.”
Broughty Ferry councillor Laurie Bidwell said: “I wrote to the council earlier this week and am waiting on an update from them.”
Conservative Ferry councillor Derek Scott said he had written to the council’s head of legal services asking him to expedite the issue so it is resolved as soon as possible.