A North Yorkshire couple were stunned to return from holiday to discover that the terraced cottage adjoining theirs had been razed to the ground.
Joan and Geoff Peel, who are both in their seventies, have now been told that their own Grade II-listed home is now too dangerous to live in and that they will have to be rehoused.
The roof of their dining room - which was located underneath their neighbour's bathroom - has been removed, and the outside wall of their lavatory replaced by a plasterboard sheet.
Craven District Council had granted listed building consent for two rear extensions to be demolished and replaced at the neighbouring house - but that was as far as the permission went.
"On Thursday, April 28, the council received complaints about works to Nutter Cote Farm, a Grade II listed building," a council spokesman tells the Craven Herald.
"Officers immediately attended the site and are now undertaking an investigation into the unauthorised demolition."
Property owners that carry out unauthorised demolition are playing with fire, and can end up with serious costs.
Last year, developers pulled down a popular pub in London's Maida Vale, the Carlton Tavern, despite the fact that planning permission had been refused. However, the local council has now ordered that the developers rebuild the pub exactly as it was before.
Earlier this year, a category A-listed house in Glasgow's west end was also demolished without permission, shocking neighbours in the historic street. Glasgow City Council is considering what action to take.
More usually, owners of historic buildings that want to demolish them simply let them fall into disrepair instead in the hope - often justified - that if things get bad enough, they'll be allowed to knock them down.
However, councils have the right in these circumstances to serve a Listed Buildings Repairs Notice forcing the owners to bring buildings up to scratch and as a last resort, can make a Compulsory Purchase Order.