Under the Childers Reforms it amalgamated with the 108th (Madras Infantry) Regiment of Foot to form the Royal Inniskilling Fusiliers in 1881.

[14] It also took part in the Battle of Havana in June 1762 during the Anglo-Spanish War: the regiment suffered heavy losses and was evacuated to New York.

[15] In September 1775 the regiment returned to North America to take part in the American War of Independence,[15] but as the result of the alliance formed by the French with the American colonists, it again found itself involved in numerous expeditions against the French West Indian possessions.

[16] In 1796 the 27th took Saint Lucia from the French, and its regimental colour was displayed on the flagstaff of the captured fortress at Morne Fortune for an hour before being replaced by the Union Jack.

[17] The 27th Regiment served throughout the Napoleonic Wars including in Egypt where it formed part of Sir Ralph Abercromby's force that fought the Battle of Alexandria against the French in March 1801, the 2nd Battalion formed part of the garrison of that city after its capture.

[18] The 1st Battalion entered the Peninsular War in November 1812[19] and participated in the Battle of Castalla[20] and the Siege of Tarragona, both in 1813.

It became part of Arthur Wellesley, 1st Duke of Wellington's army and fought at many of the key battles including Badajoz in March 1812, Salamanca in July 1812, Vitoria in June 1813 and the Pyrenees in July 1813 before pursuing the French Army into France and fighting them at Nivelle in November 1813, Orthez in February 1814 and Toulouse in April 1814.

At this period, the 698-strong battalion was deployed in square at the point where the Ohain road crossed the Charleroi to Brussels highway.

At a range of 300 yards (270 m), the French artillery caused the unit enormous casualties within a short time.

At the time of Waterloo, the soldiers of the 27th were dressed in red, short-tailed jackets, overall trousers, and a high-fronted shako.