The present house at Plas Newydd is largely a C18 Gothick mansion, developed in three main phases, incorporating an earlier building, and with significant early C20 remodelling. The history of the house can be traced in documentary sources from c1300, but the first recorded house on the site was a hall-house built in the early C16. It was to this house that Sir Nicolas Bayly added a semi-circular turret in the middle of its E front, and an octagonal tower at the SE corner in 1751-3: Pictorial evidence suggests that these additions were accompanied by remodelling work to give a consistent picturesque Gothick style to the house (including embattled parapets, arched and quatrefoil windows as depicted in Moses Griffith's watercolour of 1776). This Gothick character was taken further in subsequent phases of work: The first of these was undertaken between 1783 and 1786 by John Cooper of Beaumaris, for Henry, Lord Paget (son of Sir Nicolas Bayly) and involved the addition of a second octagonal tower to the N end of the E front (thus making this elevation symmetrical), and remodelling the rooms behind this facade. Pictorial evidence suggests that the house was re-windowed at the same time, again in a spirit of regularity and symmetry. Between 1793-99, Lord Paget employed James Wyatt and Joseph Potter of Lichfield to create an entirely new entrance front to the W (on the site of the original great hall), with a series of interiors in the Neo-classical and Gothick styles. Potter added the N service wing in 1805, completing this phase of development. The final phase of change to the house took place in the 1930s for the 6th Marquess, by H.S. Goodhart-Rendell, architect: The effect was to give a more stripped down appearance by removing the battlements from the parapets, shortening the pinnacles; the house was again refenestrated with small paned windows. The north wing was completely re-built, with the Gothick windows of the chapel being replaced by square-headed windows to match the main block. The theatre was converted into a long dining room, decorated by Rex Whistler between 1936 and 1940. On the W side, the wing to the S of the Music Room was altered, and the domestic wing was brought forward, lessening the distinction between the two buildings and altering the symmetry of the building. A screen wall was also built on the N side of the Music Room, designed by Rex Whistler. Much of the house interior was re-decorated in the 1930s by Sybil Colefax. The house was sub-divided in 1947 when the H.M.S. Conway Training School was established at Plas Newydd, with the N wing being used by the school, as well as the stable block and harbour. In the 1950s a training school was built to the N of the house, now called the Conway Centre. The school is now leased to the Cheshire County Council as an education centre, including the stable block and N wing of the house. In 1976 Plas Newydd was given to the National Trust by the 7th Marquess of Anglesey.