A pensioner was left so enraged about his neighbour's new wall that he decided to take matters into his own hands and drill holes into it.
Frustrated Ewen Taylor, 87, claims the wall encroaches on his garden by a couple of inches.
After drilling holes into it, the Cardiff pensioner was fined £90 for criminal damage - but has continued to protest anyway.
Mr Taylor, a retired bricklayer, has lived in the house on Clare Road, Grangetown, for around 50 years and has now taken to displaying messages outside his home.
The messages are critical of his neighbours, who now say the row has left their children "embarrassed to go out".
His messages include: "You and your cowboy builder are thiefs [sic]"; "Other councils take down illegle [sic] building work"; "Will they sue me?"; and "Do not like my signs, tell the council".
The display shows the street number of the next-door family, who told WalesOnline : "It needs to stop really."
Mr Taylor said his anger was first sparked back in 2020 when the family built an extension in their back yard, removing the garden wall they previously shared and replacing it with a new one.
He claims this juts into his own garden, adding: "It's a matter of two inches but it's my property.
"Even if it was half an inch I would object."
The neighbours – a married couple with four children aged eight to 20 – deny any encroachment.
The mum, 42, said: "I have no idea why he thinks it is in his property. It is distressing, especially for my children.
"They are embarrassed to go out when people ask questions about the signs."
The family's extension pushed back their bathroom to create more dining space.
Their builders knocked down the old garden wall - which Mr Taylor described as "a random rubble wall with a cock and hen finish" – and built a concrete replacement.
"Since we moved in 20 years ago, [Mr Taylor] hasn't talked to us," said the mum.
"We hadn't had an argument or anything. This is the first time there's been any confrontation.
"Cardiff council says there's no need for a planning application for extensions of six metres and this was within six metres.
"Then after the work was finished [Mr Taylor] drilled straight through."
Mr Taylor accepts he used a drill and hammer to make holes in the wall over a period of around five months.
He also peeled off a strip of stucco from the building extension.
Four circles in the garden wall show where the family have sealed up damage.
"He would often do it in the mornings when we were out," added the mum.
"One time when we were in he started doing it and we asked why. He said: 'It is in my property.' It was intimidating for my children."
In response, Mr Taylor told WalesOnline: "I don't see how it was intimidating.
"Hammering and drilling have been going on next door for years. And that's acceptable. If they want to hang new cupboards up they can hang new cupboards up.
"My wife would always hear it and say: 'They've bought another box of nails.'
"She passed away quite a few years ago."
Police handed Mr Taylor a £90 fine last September for criminal damage.
The fixed penalty notice reads: "Caused damage to neighbour garden wall with hammer breaking cement of wall intentionally."
The mum said: "The police took away his drill. That's when he started with the signs.
"We called the police two weeks ago and they said they can't do anything because it's in his private property.
"They said it is like a protest sign even though it's got our house number and he's calling us thieves. How can that not be offensive?"
Mr Taylor invited WalesOnline onto his property and gave a demonstration where he measured the width of an inside section of his house close to the garden wall.
He then walked out to his yard and measured the distance between the garden wall and a line running parallel to the edge of the same inside section.
He said the second distance was about two inches shorter, which he claims to show an encroachment on his property.
The pensioner felt he was left with "no other choice" but to drill holes after the council refused to intervene.
One council officer wrote to Mr Taylor that the extension did not need planning permission and that boundary disputes are not planning matters. This would be a civil matter, he told Mr Taylor.
The response did not satisfy the former bricklayer who showed WalesOnline photocopies of eight letters he wrote demanding council action.
Mostly written in black felt-tip and in large capital letters, the messages claim: "The issue is the illegle [sic] building work".
One reads: "Two years [council officer's name], two years of being ignored by you. Why?"
Mr Taylor said he launched his protest because he cannot afford civil action.
He added: "I am protesting that they have encroached on my property to extend their property, devaluing my property.
"I am a victim and I am penalised?"
When asked if he tried to speak with his neighbours about his concerns he said: "Oh no. How do you talk to someone and tell them what they have done is illegal?"
When WalesOnline informed Mr Taylor that the family feel harassed by the placards he said: "My signs are the truth. A couple of days ago the law [police] were here.
"They told me the signs are not very nice and that other people object to them.
"But I wasn't asked to take them down because they don't have the power. It's on my property."
The family said police have advised them they could launch civil proceedings over the display but they decided against it to avoid legal costs.
A council spokesman said it was a civil matter between two parties, adding: "We could only get involved if the signs were on the highway, causing an obstruction, or have been put up without permission, so in effect flyposting, which is an offence under the Environmental Protection Act 1990."
A South Wales Police spokesperson told The Mirror: "This is a civil dispute between neighbours in relation to building work and there is no current criminal investigation.
"In August 2021, a fixed penalty notice was issued for damage caused to a garden wall.
"The local Neighbourhood Policing Team has visited the premises a number of times and given advice to both parties."
