Under the Childers Reforms it amalgamated with the 42nd Regiment of Foot to form the Black Watch (Royal Highlanders) in 1881.

[6] It went on to form part of the storming party at the siege of Seringapatam in April 1799 during the Fourth Anglo-Mysore War[7] before returning to England in July 1806.

[9] The battalion's role was to ensure the newly appointed New South Wales Governor Lachlan Macquarie was able to govern after the previously appointed governor William Bligh was deposed by leading members of the New South Wales Corps (102nd Regiment of Foot) in the Rum Rebellion.

The 73rd Regiment was under the command of Maurice Charles O'Connell who married Mary Putland, the widowed daughter of William Bligh in May 1810, which created ongoing tension with the leaders of the Rum Rebellion (such as John Macarthur) who were highly influential members of society within New South Wales.

To reduce these tensions, the main body of the battalion left New South Wales in April 1814 on the General Hewitt for Ceylon.

[10] During the tour in Ceylon the battalion was under the command of Lieutenant Colonel Andrew Geils, whose children, along with hundreds of wounded men of the regiment, perished in May 1815 in the wreck of the Arniston after visiting him there.

[15] In 1815 the battalion joined Wellington's Army in Belgium: the regiment was in Major-General Colin Halkett's Brigade in Lieutenant General Sir Charles Alten's 3rd Division.

[22] In 1852 a detachment from the regiment departed Simon's Town aboard the troopship HMS Birkenhead bound for Port Elizabeth.