The tower commemorates the 3rd Marquess of Londonderry, who was born Charles William Stewart in 1788. He fought in the Napoleonic Wars. He became married twice first Catherine Bligh and then Frances Anne Vane. At his second wife was a rich heiress and the marriage contract obliged him to change his surname to hers, which explains why he was first called Stewart and later Vane. He succeeded his half-brother Viscount Castlereagh as marquess in 1822 and became owner of the family estate in County Down. The estate's great house, Mount Stewart, became his Irish residence but after his second marriage he lived mostly in England.