In 1832 Ellin Williams (1809-1876) became the wife of The Honorable William Owen Stanley (1802-1884) of Penrhos, MP for Anglesey 1837-1847, for Chester 1850-1857, and for the Anglesey Boroughs 1857-1874, and Lord Lieutenant of Anglesey 1869-1884. There is a slate plaque on the tower which reads, "Twr Ellin, erected in 1868 by Ellin, Wife of the Honble W Owen Stanley MP, of Penrhos. May all who visit this place bless her memory. Bendithied pawb a ymwelant a'r lle hwn ei choffadwriath." See
http://jura.rcahms.gov.uk/cadw/cadw_eng.php?id=5713 for architectural details. After years of neglect the tower was restored by the Royal Society for the Protection of birds as a bird observatory. It stands right on Northing 82, so part of the building is in the next square.