The Windsor-Clive family were one of the major landowners in the Cardiff area. Their estate, known as the Plymouth Estate, included lands in Flintshire, Hampshire, Worcestershire and Cheshire as well as Glamorgan. The Glamorgan seat of the family was St Fagan’s Castle and their lands in Glamorgan included the land on which Penarth and Grangetown, Cardiff were built.
In 1833 the 6th Earl of Plymouth, Other Archer Windsor, died without children. His sisters, Maria and Harriet, became co-heiresses of the Plymouth Estate. Harriet had married the Hon Robert Henry Clive on 19 October 1819. He had a political career and served as MP for Ludlow from 1818 to 1832 and South Salop from 1832 to 1854. He also served as Under Secretary of State for Home Department in 1818 to 1822. He died in 1854, and in the following year Harriet was granted the title Baroness Windsor. She also changed her name to Windsor-Clive at this time.
Harriet and Robert had six children, and the eldest son and heir was Robert Windsor-Clive. He died aged 35 in 1859, leaving his infant son, Robert George Windsor-Clive, as the heir to the estate.
Baroness Windsor petitioned against the Bute Dock bills. A number of people gave evidence on her behalf, including James Tomson, her agent, and George Herbert Windsor-Clive, her middle son. The Windsor-Clive family was involved with plans to build docks on their own lands at Penarth. Work began on these in 1859, and the first docks were completed in 1865. Baroness Windsor was motivated to ensure that her own docks project was not adversely impacted by Bute’s rival development in Cardiff. Ultimately although her opposition to the development of Cardiff docks failed, the Penarth Docks were able to compete and proved successful. In 1913, the peak of the Welsh coal trade, 4,660,648 tonnes of coal were shipped from Penarth Docks.