The purchase of €11 million comes after a full Value for Money assessment and an independent commercial valuation, and has received formal approval from the Department of Public Expenditure.
The State has purchased some 235 acres of historic estate lands at Castletown House in Celbridge - a move that could end years of access problems at the historic estate.
The lands have been purchased at a price of €11.25m.
The OPW began the acquisition process earlier this year, commissioning a revised valuation report and business case, and appointing Lisney as its commercial agent.
After what officials describe as “intense and confidential” negotiations, agreement was reached on a price of €11.25 million - a figure formally approved by the Department of Public Expenditure.
Lisney had advised that the market value of the lands stood at between €7.25 and €7.5 million in September, but the OPW says the higher price reflects the strategic importance of the purchase.
According to the OPW, the State will sometimes pay above market value for assets that protect heritage, enhance adjoining public lands or secure long-term strategic access.
It says the Castletown acquisition safeguards the wider historic demesne, enables alternative vehicular access to the estate, and ensures expanded public access to parklands for communities in north Kildare.
In total, the area in State ownership and in the care of the OPW now encompasses some 462 acres of demesne lands and parklands at Castletown and 19 acres at Donaghcumper.
The newly acquired lands will be integrated with lands and property already in the ownership of the OPW, which includes the Palladian mansion Castletown House, 227 acres of woodlands and Donaghcumper House, farmyard and walled garden to the south of the river Liffey.
The Castletown lands were sold for €5 million in 2023.
Kildare North Social Democrats TD Aidan Farrelly said it is a "wonderful day".
He said campaigners worked "tirelessly".
He said a master plan will be developed in partnership with the community to ensure that the "full potential of the site is brought to fruition".
Social Democrats Cllr Claire O' Rourke said locals are "overjoyed".
In 2023, after adjoining lands changed hands privately, the entrance and car park beside the M4 were shut off.
In July, Castletown House Parklands reopened after a meeting involving the OPW, Minister Kevin “Boxer” Moran, Gardaí, local representatives and community groups.
This evening, Minister Moran stated: “When I became Minister for the OPW in February this year I had three objectives in relation to Castletown. The first was to get the OPW staff back to their place of work, this was achieved in April of this year. The second was to re-open the House and parklands again to the public, this was achieved in July this year and the house re-opened for tours over the summer. I was also committed to resolving the vehicular access issue."
He added: "I am delighted to confirm today that this third objective has now been achieved through the purchase of the lands, which includes the access from the M4 motorway. In announcing this I would like to thank the OPW staff that work at Castletown for their dedication and resilience over the last couple of years. I look forward to continuing to work with the local elected representatives, Kildare County Council and the local community in the weeks and months ahead."
He said the OPW is committed to restoring access to the Castletown Estate via the M4 access "as soon as possible" and in the coming week will assess what remedial works, if any, are required in order to facilitate this.

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