Dromoland Castle has won a planning battle to install a new water supply as part of a €16m upgrade - despite opposition from neighbour Lord Inchiquin who claimed it would devalue his estate.
An Bord Pleanála has given the five-star hotel in Co Clare permission for the vital part of the redevelopment, in spite of the protest from Conor O'Brien, chief of the 75,000-strong O'Brien clan.
"We are delighted with the decision. It is a vital piece of the major refurbishment going on here right now," said Dromoland general manager Mark Nolan.
Mr Nolan said that there has never been such investment in five-star hotels in Ireland and added: "We believe the €16m is money well spent. The hotel property is being restored to its former glory with the help of a fabulous historical architect." Mr Nolan said the year ahead "looks very sold - it is very promising".
The Inchiquins sold on Dromoland Castle in 1962 and today live in Thomond House on adjoining lands.
In his appeal against the Clare County Council decision to grant planning for the water supply, Lord Inchiquin told An Bord Pleanála that his estate will be substantially devalued as a result of conditions imposed by the council connected to the planning permission.
Lord Inchiquin stated in his appeal that the conditions attached to the permission "would cause the sterilisation of my farmland".
He said that the plan would also "cause a total restriction on my farming practices such as the spreading of slurry and fertilisers and would prejudice and disrupt my entire farming enterprise and cause serious economic difficulty and would seriously affect the value of my agricultural lands and substantially devalue my entire estate".
The 18th Baron Inchiquin also argued in his appeal that "the storage tanks and facility pumping houses and treatment facility will impact adversely on my property and residence being adjacent and located near my residence".
Lord Inchiquin also told that the board that pumping houses and treatment facilities "will cause noise pollution and its location is entirely inconsistent with the integrity and aesthetics of Thomond House and also Dromoland Castle which is of national architectural and historical importance".
The Lord claimed: "Its proximity to my residence will adversely impact upon the integrity and value of my home and land."
It is not the first time that Lord Inchiquin has been in conflict with Dromoland Castle. In 2012, the High Court refused an application for Dromoland Castle to return to him 37 paintings valued at €1.4m.
The board inspector in the planning case said that based on the nature, scale and location of the proposed development to adjoining dwellings, he did not consider it would have any impact on residential amenity.
The board stated that it would not have a significant negative impact on the groundwater resources in the area.