Complex sentence: In 1822 its title was altered again when it reroled as a Lancer regiment, become the 17th Regiment of (Light) Dragoons (Lancer) and the following year it returned home and on its journey discovered this change.
Split into simpler sentences: In 1822 its title was altered again when it re-roled as a Lancer regiment, becoming the 17th Regiment of (Light) Dragoons (Lancer). The following year the 17th returned home and on its journey discovered this change.