He returned to service in 1790 serving on the frigate HMS Proserpine on the Jamaica Station and fought at the Battle of Martinique and Invasion of Guadeloupe in 1794.

He was promoted to captain in 1796 and afterwards joined the ship of the line HMS Sans Pareil, from which he was sent to become lieutenant-governor of Curacoa Island in 1800.

After this he joined the newly formed Woolwich Division of Royal Marines and slowly received further promotion, becoming a colonel in 1830.

He then served as an aide de camp to King William IV in the following year and became colonel commandant of the Chatham Division, a position he held until 1837.

To further difficulties, Seymour quarrelled with the army's Major-General Sir Thomas Trigge over who Tremenheere owed subordination to, he being an anomalous Royal Marine.

Trigge attempted to replace him as lieutenant-governor with Lieutenant-Colonel William Carlyon Hughes, but Tremenheere refused to give up his position to him.

[8] In 1801 Seymour died, giving the upper hand to Trigge who finally succeeded in installing Hughes and removing Tremenheere in 1802.

[5] On 28 December of that year he was made an aide de camp to King William IV, the first Royal Marine to hold that position.