The battle lines have been drawn at Belgrave Square in Monkstown, Co Dublin, with residents announcing a 24-hour "watch" to ensure no development work starts in the gardens in the centre of the square.
The gardens, which date from 1860, were the subject of a dispute earlier this week between residents and excavation contractors who moved in without notice.
"Next time we won't be caught out," said Mr Ed Boyne, of the Belgrave Square Residents' Association, which has set up a "digger-watch" rota involving 42 householders in the square and a further 50 in the locality.
"There are four points of watch at the different ends of the square and each one will be monitored in the hours of daylight. At night-time, certain residents have agreed to keep an ear out for chainsaws. There are numbers to call and procedures to follow if there is another incursion."
The gardens were sold recently to a Navan builder, Mr Eugene O'Connor, who outbid the residents' tender for the 2.5-acre gardens. The land is zoned for open space/amenity use in the Dun Laoghaire Borough Development Plan which is currently under review.
Contractors arrived at the gardens with excavating equipment on Monday and began to take soil samples. However, after some confrontation with the residents they left.
Mr O'Connor could not be contacted by telephone yesterday.
Mr Boyne said the residents were determined to preserve the access to the gardens which they have traditionally enjoyed. While they were prepared to fight any potential planning application for development of the square, they were "equally concerned that excavation and clearance will destroy the square even before the planning battle starts".
He said "the character" of the square depended on the gardens, which contain a playground. "There are concentric hedges shown on a map dated 1860. Those hedges are still there, along with trees as old as 200 years. It would take no more than two hours to clear the lot." The residents have also taken legal advice on the validity of their claims for right of access.
Commenting on the situation, Mr Willie Murray, county planner with Dun Laoghaire-Rathdown County Council, said it was the council's intention to continue the present zoning of open space/amenity use in the new draft development plan which he said was due to be adopted in the immediate future.
"It would be our intention to protect the square from development," he said.