:Plas Machynlleth

Plas Machynlleth is known to have existed since the seventeenth century. The house was called 'Greenfields' for many years, but was renamed after the town by 1888.{{cite web |author1=Maritime Officer |title=Site Record 29818 |url=https://coflein.gov.uk/en/site/29818/ |website=Coflein |publisher=Royal Commission on the Ancient and Historical Monuments of Wales |access-date=2 July 2025 |archive-url=http://archive.today/2025.07.02-141126/https://coflein.gov.uk/en/site/29818/ |archive-date=2 July 2025 |language=en |date=June 2015 |url-status=live}}

The property was bought by John Edwards, a local solicitor, in the 1750s. By 1765, a three-storey double-pile{{efn|'Double-pile' means a house that is two rooms deep.{{cite web |author1= |title=double-pile house |url=https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095728243 |website=Oxford Reference |publisher=Oxford University Press |access-date=3 July 2025 |archive-url=https://web.archive.org/web/20241127070759/https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095728243 |archive-date=27 November 2024 |language=en |url-status=live}}}} house had been built on the property; this now forms the core of the building. Edwards died in 1789; his son, Sir John Edwards, 1st Baronet, retired from politics in 1841 and undertook extensive improvements and remodelling of the house, including the addition of several wings, a new façade and a portico. On his death in 1850, Sir John Edwards' estate passed to his daughter, Mary Cornelia Edwards. She had married George Vane-Tempest, 5th Marquess of Londonderry, in 1846; as a result, the house became the main residence of the 5th Marquess until his death in 1884. His eldest son Charles left Machynlleth on succeeding to the Marquessate, and the house was then lived in by Charles' youngest brother, Lord Herbert Vane-Tempest.

After Lord Herbert was killed in the Abermule train collision on 26 January 1921,{{cite news |title=Court and Society |author= |work=Belfast News-Letter |date=1 February 1921 |url=https://www.britishnewspaperarchive.co.uk/viewer/bl/0000038/19210201/078/0005 |url-access=registration |page=5 |via=British Newspaper Archive}} no family members remained at the house; many of the Londonderry family's landholdings were sold in 1931, and Plas Machynlleth was closed throughout the 1930s. During the Second World War, the house was used as a girls' school. In 1948, the Charles Vane-Tempest-Stewart, 7th Marquess of Londonderry, a prominent Ulster Unionist politician, gave the mansion and its estate to the town. The building was adapted for use as council offices, while the {{convert|40|acre|ha|abbr=off|adj=on}} grounds were designated as a public park.

In 1995, after a £3 million refurbishment funded by Montgomeryshire District Council and the European Union, the building became the 'Celtica' heritage centre. It also had space to host conferences. For several years the centre was successful in attracting tourist and educational visits and conferences. The mansion was taken over by the new unitary authority, Powys County Council, in 1996. With little investment by the council and with declining visitor numbers, the council decided to close the centre in 2006. It cited a loss of £1.1 million between 1998 and its closure.{{Cite web |author= |url=http://news.bbc.co.uk/1/hi/wales/mid/4219616.stm |title=Celtica attraction set to close |access-date=13 June 2007 |website=BBC News |date=6 September 2005 |archive-url=https://web.archive.org/web/20250419100428/http://news.bbc.co.uk/2/hi/uk_news/wales/mid_/4219616.stm |archive-date=19 April 2025 |url-status=live}} The Plas is now used as a community and meetings venue. The gardens are listed at Grade II on the Cadw/ICOMOS Register of Parks and Gardens of Special Historic Interest in Wales.{{NHAW|uid=342|num=PGW(Po)26(POW)|desc=Plas Machynlleth |class=HPG|access-date=6 February 2023}}

Other residences of the Marquesses of Londonderry:

• Londonderry House in London
• Mount Stewart in County Down
• Seaham Hall in County Durham
• Wynyard Park in County Durham
• Woollet Hall in Kent
• Garron Tower in County Antrim

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{{Commons category|Plas Machynlleth}}

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Category:Country houses in Powys

Category:Grade II* listed buildings in Powys

Category:Registered historic parks and gardens in Powys

Category:Machynlleth