Melin Llanddyfnan aka Pen y fan Llanddyfnan · Isle of Anglesey · Wales

Melin Llanddyfnan stands in an elevated position south-east of a country road leading to Llanbedrgoch from the B5110 out of Llangefni, within the grounds and about half a kilometre north-west of Plas Llanddyfnan. It is also known as Pen y fan.

The site has one of the earlier recorded windmill histories on Anglesey. The earliest record is an estate map of 1746. A later estate map of 1748 shows a windmill on the site, and in March 1749 William Bulkeley recorded in his diary that a previous post mill had burnt to the ground. The present tower mill is associated with a date of 1750 carved on an interior beam, suggesting construction shortly after the loss of the earlier post mill.

The later tower belongs to the group of eighteenth-century Anglesey windmills built during the period of expanding windmill construction in the 1730s and early 1740s. The tower is circular, full height, and three storeys high. It is built of coursed rubble masonry and rendered. Original window openings have slate sills and now contain metal-framed casement windows, with one window infilled with brick. The doorway has been enlarged and fitted with modern boarded doors.

The mill was known to have been working at the turn of the twentieth century, but it appears to have ceased production soon afterwards. It was marked as Old Windmill on the 1918 one-inch Ordnance Survey map. The tower then became roofless and derelict until the 1950s, when its owner, Francis Wilson QC, the Recorder of Chester, restored it principally for use as a viewing platform. The interior was not inspected at the time of the Cadw survey, but it was said not to contain original mill machinery and to have a staircase leading to the viewing platform on the roof.

Melin Llanddyfnan was listed at Grade II on 12 May 1970. It was listed, notwithstanding alterations, as a substantially intact windmill tower, one of the surviving full towers on Anglesey and one of the earliest recorded windmills on the island.