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Merthyr Mawr House


Merthyr Mawr House has a small and attractive early-19th-century landscape park. Contemporary pleasure grounds with some good specimen trees and shrubs include an area on a hill behind the house which incorporates a small chapel. There are formal and informal gardens around the house. On the site of the earlier house are the remains of the walls of earlier garden compartments dating from the 16th or 17th century.

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John Nicholl, born in 1759, was the creator of the landscape at Merthyr Mawr. Nicholl had a successful career in law and parliament, and was knighted in 1798. He bought the estate in 1804, with the intention of creating an impressive monument as the foundation of his own dynasty. This seems to have been achieved, and the seventh generation of the family is now incumbent in the house at Merthyr Mawr.

Sir John Nicholl played a large role in designing the house and grounds, and was widely read on horticultural subjects. Work on the new house began in 1806. Plans of the area dating to 1794 and 1812 demonstrate the emparkment of the estate, which had previously consisted of a block of 17 fields. The old manor house was demolished and its materials re-used, but the orchard and walled gardens of the old manor were retained. The produce from these areas was added to by that produced in the new kitchen garden.

The new house was very deliberately placed to take advantage of attractive landscape features, without the need to spend vast sums creating them. On offer in the locality were the ruins of Ogmoe Castle, Coity Castle, the local village, the Ogmore river, the ruined chapel of St. Roque and caverns formed by an underground stream. Vistas to all these features were integrated into the layout of the house and grounds.

Major expenditure was necessary for a new road to the village, as the old one brought the locals too close to the manor. The new road had to cross the river, and Nicholl chose a cheap wooden structure which was built in 1808 and was in poor condition by 1827. Nicholl was obliged to replace this with a stone bridge, against his will, but the structure is still termed ‘The Wooden Bridge'.

The majority of the laying out and planting of the park and pleasure grounds was undertaken in 1808 and 1809. In 1808, Nicholl noted that 25,003 plants of 42 species were to be transplanted. Shrubs, trees, orchard trees and climbers were all ordered. The majority of the trees were standard forest varieties, but fifteen species of ‘ornamental and special trees' were ordered in November 1808. Some landscaping was also undertaken to even out the slopes around the sides of the house.

Garden buildings were the next priority. Murray A. McLaggan notes (in Hilary Thomas' book, see references) that in 1808, men were ‘Hauling stones for ye Bathing House', ‘making holes in wall of House to receive ye verandah' and building the greenhouse and making Walks. In 1811 the ‘Beehouse' and ‘Dovehouse' were added. The ‘Laboratory' and ‘Icehouse' followed in 1813, then in 1814 the ‘Garden Shed', ‘Piggery', ‘Grapehouse' and ‘Hothouse'. In 1816 there was the ‘Summer House' and a ‘Pit'. More greenhouses were added in 1835 and 1840. These structures are no longer extant, and for some, such as the summerhouse and bathing house, the site is unknown as well.

John Nicholl died in 1838, and succeeding generations of the family have made various additions and alterations to the house, park and gardens. The development of the gardens was taken over by succeeding generation of women in the family, some of whom came from gardening traditions. One individual, Minnie Dillwyn, was first cousin to J.D. Llewelyn, creator of Penllergare. A drawing by Minnie Dillwyn from 1867 shows the changes which had taken place since Sir John's time. Flowers have a significant role and the lawn is shown as being close-cut, following the invention of the lawn mower. Another significant change was the addition of a ha-ha, the date of which is unknown. It was complete by 1876. Prior to this date, terracing was added in front of the house (possibly in the 1850s) and the wood behind the house was extended to the west. In the 1850s, grounds for cricket and archery were created, and later areas for lawn tennis and croquet.

Three gardeners were employed at any one time between 1835 and 1875. This doubled under the ownership of Minnie Dillwyn's eldest son, John. During the early-20th century, retaining walls were built for the terraces, with borders and stone steps. The middle terrace was converted to a bowling green, long borders were created south of the walled garden and new gravel paths were instituted. A bamboo garden was laid out between the road and the river, but this was neglected in the war and is now impenetrable. A new greenhouse was added in 1900, which is still in good repair, and a small summerhouse was a further addition.

During World War 2, the house became a home for convalescent servicemen, and though the kitchen garden was well-utilised and kept in good repair, other areas were barely maintained. The gardens were simplified in the 1960s. The kitchen garden was put to more ornamental uses, the rockery had already gone and the tank garden was removed. A landscaped swimming pool garden was created, and woodlands were restored and extended. A new generation of the family took over in 2005.

Associated People
Features & Designations


  • CADW Register of Landscapes Parks and Gardens of Special Historic Interest in Wales

  • Reference: PGW(Gm)12(BRI)
  • Grade: II*
  • Scheduled Ancient Monument

  • Reference: Chapel Hill camp (Gm 248)
  • Scheduled Ancient Monument

  • Reference: Merthyr Mawr inscribed stones (Gm 26)
  • Scheduled Ancient Monument

  • Reference: St Roque's chapel (Gm 247)
  • CADW Register of Listed Buildings in Wales

  • Reference: Lodge
  • Grade: II


  • House (featured building)
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  • Greenhouse
  • Description: A glasshouse built by Skinner Board & Co from Bristol.
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  • Kitchen Garden
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  • Ha-ha
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  • Garden Terrace
  • Description: Terraces in front of the house. The date is postulated rather than known.
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  • Bowling Green
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  • Tennis Lawn
  • Croquet Lawn
  • Planting
  • Description: A bamboo garden was laid out between the road and the river, but this was neglected in the war and is now impenetrable.
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  • Description: A landscaped swimming pool garden was created.
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Key Information





Principal Building

Domestic / Residential



Open to the public


Civil Parish

Merthyr Mawr