The Blakeys, who live on Station Road, said two years ago the wall - which their home overlooks - was virtually clean and they blame yobs for ruining the local landmark, thought to have stood for more than a century.
And, according to residents Estella and Gordon Blakey, illegal spray painting is just one aspect of the anti-social behaviour plaguing Llandaff North in Cardiff.
Mrs Blakey, 65, said: 'The wall is absolutely covered in graffiti and you often see children drinking alcohol on a bench nearby.
The Royal Mail is to fit a post box at the end of the Blakeys' drive to rule out any chance of Spike, who will be kept in the kitchen at the back of the property, spotting postal workers.
The company, which said at the time it was a rare move but forced upon it because of the layout of the houses, began deliveries again last Tuesday after a deal had been struck with the Blakeys.
Mr Blakey, aged 36, who said his pet had never mauled anyone before, said: "We've got to keep him away from doors and windows.
Mrs Edith Thompson, aged 74, who lives close to the Blakeys, said: "This has gone on for too long and seems a bit silly now.
Two weeks later, Royal Mail bosses ordered deliveries to 18 houses in the street should be suspended until it received assurances from the dog's owners, Mr Derrick Blakey and his wife, Eileen, that their pet, Spike, would not be let loose during delivery times.
Mr Blakey, aged 36, said he was stunned by Royal Mail's actions and sympathised with his neighbours.
Mr Blakey, a service engineer, said he was asked by the Royal Mail to send assurances Spike will stay in the house while deliveries are made.