Built in 1731, it was likely designed by Sir Edward Lovett Pearce and completed by Richard Cassels in the Palladian style, although Sir John Vanbrugh, who was related to Pearce and with whom he trained, is thought to have also influenced the design of the house, which could be seen by the Baroque details, great arched chimney stacks and the palatial grandeur and scale.

They owned vast amounts of land in counties Meath, Westmeath, Cork, Londonderry, Antrim, and Dublin as well as in Devon and Cornwall in England.

[3] In 1661, Sir Hercules Langford, 1st Baronet bought Lynch's Castle located on the Summerhill demesne in County Meath and many other townlands from The Rt Rev.

Earlier, John Rowley came to Ireland during the reign of James I, as sole agent for the building of the towns of Derry and Coleraine for the London Society.

[8] At the same time he was also commissioned to complete an extension to the already sprawling Summerhill house however these designs composed of a quadrant link connecting two wings, were ultimately never executed.

In 1922, Colonel The 6th Baron Langford (1849–1931), who had only inherited the barony the previous year, sought compensation from the Government of the Irish Free State.

After three years of negotiation with the Compensation Board, a sum of £43,500 was paid to Colonel Lord Langford, approximately one third of the value of the house and contents destroyed in the fire.

Four semi-columns with Corinthian capitals ornamented the front; the main order was carried up the full height of the house like Renaissance Palaces in Rome.

The Lafranchini brothers are said to have designed some of the interior stucco work and ceilings of the house including the state dining room which was detached from the main block.

The hall contained plaques, pastels and oil portraits by Francesco Guardi and Hugh Douglas Hamilton as well as statuary of Mary Pakenham, daughter of the first Lord Longford by the sculptor Thomas Banks.

The drawing room had a southern aspect, and contained several portraits of the Rowley family including by famous artists such as Pompeo Batoni.