Emergency work carried out to save historic mansion

Dale Spridgeon, Local Democracy Reporter

Emergency work has been carried out at a derelict 18th-century Welsh mansion after years of neglect left the historic building in poor condition.

Plas Nannau, a Grade II* listed mansion at Llanfachreth near Dolgellau in Eryri, has now been made watertight, allowing the building to begin drying out after years of water ingress.

The mansion, completed in 1796 in the shadow of Cadair Idris, stands on an historic estate famously associated with Owain Glyndŵr and a tale of attempted murder, revenge and a supposedly haunted oak tree.

It was once at the centre of one of the largest estates in Merionethshire, with the estate’s origins dating back to the 12th century, but fell into serious disrepair.

Its deterioration accelerated in 2019 when thieves stripped tonnes of lead from its roof.

Members of Eryri National Park Authority were given an update on the condition of the building at a planning meeting on Wednesday, September 9.

According to the Royal Commission on the Ancient and Historical Monuments of Wales, one of the best-known stories associated with Nannau concerns Hywel Sele and his relative Owain Glyndŵr.

The Royal Commission states: “One of the most famous stories told in its long history was the alleged assassination attempt by Hywel Sele of Nannau on his relation Owain Glyndŵr.

“Hywel drew his bow to shoot a deer but quickly turned and aimed at his cousin instead. Owain was wearing chain mail under his shirt and survived.

“He is then said to have killed Hywel Sele and put his body into a hollow oak tree.

“This oak tree became known as Ceubren yr Ellyll (the haunted oak) and many ghost stories were told of its powers until it was struck by lightning in 1813.”

Watertight

In a report to members, Jane Jones, principal planning officer for compliance, said discussions over the mansion had continued following a site meeting in December 2025.

She said: “Emergency works to make Nannau watertight have taken place. These works have prevented any further water ingress into the building, and it is now able to start drying out.

“Nannau has also been emptied of chattels with any items relating to Nannau being stored in a large on-site container.

“A pre-application enquiry has been received and responded to, and although a large quantity of information is required before informing a substantive response; this submission has resulted in an on-site meeting with a representative from CADW.

“The authority now awaits additional details to provide a full response to the pre-application enquiry.”

Showing councillors images of the property, Ms Jones described the condition in which it had been found when work began.

She said: “When they went in January to start works they took drone footage going round, showing the state of the building before they started work and it was pretty poor.

“Internally, the actual main staircase going up to the second floor has actually fallen down.

“Now, the only access to the building is through the front door, but you can’t access the second floor, so scaffolding has been put up around the building to gain access through a first floor window.”

Slates

Ms Jones said the roof had been made watertight, with slates removed and stored for future use and re-felting planned.

She said: “Water ingress has now stopped completely, whereby during the summertime when we have accessed the building, it is quite clear it is already starting to dry out, which is obviously what we needed to do.

“A pre-application inquiry is now in, and discussions are ongoing with the agents. Hopefully there will be more progress moving forward.”

Cllr Delyth Russell, who represents Brithdir and Llanfachreth, said there had been “so much talk about this in the community” and that it was “good to have this out in the open, now”.

She asked whether a change of ownership had altered the situation and whether the authority expected a new planning application from the new owners.

Cllr Russell also asked how much money the national park authority had spent on the property.

Ms Jones replied: “So far, everything seems to be quite promising, we are having the correct dialogue, they seem amenable regarding requests, and so on.

“Hopefully, so far, communication has been good, better than in other years. So we will have to wait and see what transpires next in terms of additional pre-application inquiries, or it may come to the application.

“Hopefully the new owners will be submitting a new application.”

She added that the authority had so far spent no money on the work, with the emergency repairs paid for by the owner.

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