The 42nd's Waterloo started on the 16th of June 1815, 2 days before the famous battle was to take place! After Napoleon had escaped from Elba and convinced his army to go against the King of France and join him in releasing terror against the Anglo-Dutch.

On the 15th of June some of the officers and soldiers from the 42nd performed at the Duchess of Richmond's Waterloo Ball in Brussels whilst the rest of the regiments prepared themselves for battle. Then news reached Wellington that Napoleon's armies were marching through France. In the early hours of the 16th of June the 42nd left almost immediately with many of the officers still in their white dress knee-breeches to confront Napoleon, marching to the tune of "Hieland Laddie". After a gruelling journey in full marching order the 42nd arrived near to the French/ Belgium border at Quartre Bras by the Charleroi Road at about 3pm on the 16th of June and entered a 5 hour battle which may have been a factor in Wellington's Army finally beating Napoleon.

Napoleon had sent out a force to deal with the Anglo-Dutch at Quatre-Bras whilst he dealt with the Prussians at Ligny hoping that it would divide the 2 forces. The French commanded by Marshal Ney arrived along the Charleroi Road after having dealt with the 79th Highlander's offensive in the valley of Gemioncourt. The Brunswick Hussars were the 1st allied force at Quatre-Bras to attack the incoming French but failed miserably as most of the Brunswickers were raw troops and had little battle experience.

The 42nd were posted on a reverse slope in a line above the road. At first sight they were amazed at the advance of the French. As the French passed the 42nd, the older soldiers of the regiment weren't satisfied and immediately opened fire and tried to restrain the French from advancing, they succeeded in causing a cessation of fire, but the Lancers were sitting to the rear of the cavalry and wheeled sharply round and advanced in admirable order directly upon the rear of the 42nd who recognized their advancing position and formed square, but just as the 2 flank companies were running to form rear rank the lancers penetrated the square. Instead of the square being destroyed by the French the lancers were either bayoneted or taken prisoner. All further attempts by the French were repelled.

On a sadder note the Commanding officer of the 42nd ( Lieut. Colonel Sir Robert Macara ) was killed and within the brief space of a few minutes the command of the regiment devolved upon 3 officers in succession, Lieut. Colonel Dick, who was severely wounded, Brevet Major Davidson, who was mortally wounded and Brevet Major Campbell who commanded the regiment during the remainder of the campaign.

The 42nd pinned down Marshal Ney and prevented him from going to Napoleon's aid at Ligny which sealed Napoleon's fate and stopped Marshal Ney's men from wiping out Marshal Blucher's Prussian army at Old Fortwartz, before the Prussian and British armies could merge together.

The 42nd lost 298 men at Quatre-Bras but were recognized in Wellington's dispatch of the battle. On the 18th of June 1815 the 42nd held the left centre of Wellington's position behind La Haye Sainte, against a French force of 13,000 bayonets. The 42nd on the day of Waterloo only lost 5 and had 45 injured. After the battle the wounded returned to their kind hosts in Brussels.