On the inheritance of the Dukedom of Norfolk in 1815 by his elder brother Bernard, Henry Molyneux-Howard in 1817 was granted the courtesy title "Lord", the style of a younger son of a duke.
In 1814, he also purchased Aldingbourne House, formerly the seat of Lady Molyneux-Howard, and made some alterations to expand it.
[3] On 14 October 1817 Molyneux-Howard resumed the use of Howard as his principal surname, becoming Henry Thomas Howard-Molyneux-Howard, and on the following day was granted a warrant of precedence to be styled as a younger son of a duke, and having thus gained the courtesy title "Lord", became known as Lord Henry Thomas Howard-Molyneux-Howard.
He carried out his duties as Deputy Earl Marshal during the planning for the coronation of King George IV (1820–1830), but was unable by reason of illness to act at the actual event, at which his role was taken by his kinsman Lord Howard of Effingham.
On 12 September 1801, Howard-Molyneux-Howard married Elizabeth Long, daughter of Edward Long (1734-1813), a British colonial administrator, historian and author of The History of Jamaica, by whom he had one son and four daughters: Howard-Molyneux-Howard died aged 57 in June 1824 after a short illness in his house in Lower Grosvenor Street, Mayfair.