Mervyn Smith's FirstCare nursing home group will claim in a looming court battle that the former owner of Howth Castle, Julian Gaisford-St Lawrence, never intended to allow a hotel at the estate to be converted into care home and instead used the proposal to leverage a plan to sell the entire Howth estate.
A deal to sell Howth Castle and its 470-acre demesne in north Dublin, which includes the hotel and golf courses on the grounds, was sealed in 2018.
The sale to Irish investment group Tetrarch Capital included Ireland's Eye, a small island close to Howth harbour.
The sale - completed in 2019 - ended the family's nearly 900-year ownership of the property.
Tetrarch, headed by chief executive Michael McElligott, plans to redevelop the hotel as a luxury property.
It also plans to redevelop the golf courses and may, in addition, seek permission to build housing on the estate.
But it has been alleged in court documents that FirstCare and other companies linked to Mr Smith struck a memorandum of understanding in 2016 with Mr Gaisford-St Lawrence, and a company connected to him, to redevelop the Deer Park Hotel at the Howth Castle demesne as a nursing home.
Mr Smith's companies claim that they incurred more than €387,000 in fees that were paid to architects and project managers as they advanced plans for the conversion of the hotel.
They have told the court that the costs associated with the plans continued to be incurred until April 2018, when Mr Smith was allegedly told by Mr Gaisford-St Lawrence that he no longer wished to proceed with the project.
Mr Smith has said that he had only read comments in 2019 made by Mr McElligott in a newspaper article the year before that Tetrarch had been working with Mr Gaisford-St Lawrence and his family for "several years" on the plan to buy the Howth demesne.
Mr Smith has said that he was unaware of any engagement between Mr Gaisford-St Lawrence and Tetrarch, that he was shocked to learn of it, and that had he known of it, he would not have sanctioned the expenditure on the nursing home project.
Last month, the High Court granted Mr Smith's companies leave to amend their statement of claim in the case.
"The plaintiffs wish to add to their case an allegation that the defendants - as the defendants' solicitor puts it - covertly negotiated for the sale of the property to someone else," noted Justice Allen, who heard the motion by the plaintiffs to amend their claim.
The motion to amend the claim had been objected to by the defendants.
Their counsel had said that the sole purpose of the application to amend the claim was to embarrass the defendants and gain access to confidential information.
Earlier this week, the court ruled that the plaintiffs were permitted to recover 70pc of the costs of the successful motion to amend the claim from the defendants.
The defendants have maintained that the nursing home project was "dead in the water" by February 2017, and that they were then free to negotiate with and sell to whomever they wished, Justice Allen noted.
"But the premise of the plaintiffs' case is that it was not so," the judge said his June ruling on the motion.
"Whether the nursing home project was or was not dead in the water in February or perhaps April 2017 will be a matter for the trial judge," he said.