The London Irish Rifles are based in Flodden Road, Camberwell, traditionally the drill hall of the 21st (County of London) Battalion The London Regiment (First Surrey Rifles). Formed in 1860, the 28th Middlesex (London Irish) Rifle Volunteer Corps was popular and numbered among its ranks the Marquises of Donegal and Conyngham, the Earls of Arran and Belmore, Lord Palmerston (who joined as a private soldier), and WH Russell of The Times.

The 21st London can trace its origins to 1803 when the First Regiment of Surrey Volunteers was formed. The 1st Surrey Rifle Corps was raised in 1859 in Camberwell and within two years had merged with the 3rd Corps. By 1861 the strength stood at eight companies and in 1881 1st Surrey became a volunteer battalion of the East Surrey Regiment. Many volunteers served in South Africa. The Volunteer Annual of 1903 notes that the Corps was recruited from the middle-classes and that introduction by a member was necessary. There was an annual subscription of 1s/6d and the head-quarters was at 4 Flodden Road, Camberwell.

On the outbreak of war, the 21st London formed two service battalions and a reserve, proceeding to France in March 1915 as part of 6th Infantry Brigade, 2nd London Division (later 47th). The 1st Battalion fought at Givenchy and Loos in 1915, Vimy Ridge and the Somme in 1916, Ypres and the Hindenburg line in 1917 and Cambrai in 1918. The 2/21st transferred from France to Macedonia then to Palestine in 1917. The Battalion suffered 1187 killed and over 6000 wounded.

In 1935 the 21st became 35th (First Surrey Rifles) Anti-Aircraft Battalion and was involved in the air defence of Britain throughout the Second World War. An air defence role continued until 1971 when a major amalgamation took place; many of the London Regiment Battalions were incorporated into 6th Volunteer Battalion The Queen's Regiment, becoming 7 QUEENS in 1975.

Re-numbered as the 16th in 1880, the "Irish" became a Battalion of the Rifle Brigade the following year. During the war in South Africa, the battalion sent eight officers and two hundred men for active service. One officer won the Distinguished Service Order and another member gained seven bars to his South Africa Medal. In recognition of their service, the London Irish were granted the battle honour of South Africa 1900-1902.

The London Irish transferred to the Territorial Force in 1908 titled the 18th (County of London) Battalion, The London Regiment (London Irish Rifles). During the First World War, the London Irish raised three battalions and the 1st Battalion went to France in March 1915 as part of the 47th (2nd London) Division. It saw its first action in May at Festubert.

In September 1915, at the Battle of Loos, the 1st Battalion distinguished itself by the capture of enemy trenches led by the Captain of the football team, Sgt Edwards who took his football and kicked it towards enemy trenches. His fellow soldiers joined in and, despite intense enemy gun fire, the ball was kicked across No Man's Land until it was finally booted into the German trenches. In a desperate and bloody battle, the London Irish captured and held their objective. The football itself is still preserved in the Regimental Museum and the memory of Sgt Edwards is commemorated on Loos Sunday.

The 2/18th also served on the Western Front where its first duty was to take over part of the line at Vimy Ridge. From France the Battalion moved to Macedonia, later serving in Palestine. There on 23 December 1917, at Khurbet Adesah, the Battalion's officers and NCOs were reduced to one subaltern and one sergeant. The 2/18th was disbanded in July 1918. The 3rd Battalion was a reserve battalion throughout the War.

In 1937, after the former London Regiment was disbanded, the "Irish" became known as the London Irish Rifles, The Royal Ulster Rifles. The Caubeen - the plumed bonnet - was adopted officially for wear by all ranks. Unlike other Irish regiments, the London Irish wear the Caubeen pulled down on the left side (instead of the right), a distinction maintained to this day.

In 1939 the London Insh was organised into two battalions. The 1st left England in August 1942 to serve in Iraq and Italy taking part in the battles for Monte Camino and Anzio. The 2nd Battalion served in North Africa and Italy.

After the War the Battalion re-formed as a Battalion of the Royal Ulster Rifles but the 1967 re-organisation of the TA reduced the London Irish to company strength. The three Irish Line infantry Regiments had combined to form the Royal Irish Rangers and the company became 'D' Company (London Irish Rifles) 4th Bn The Royal Irish Rangers, remaining so until the re-formation of The London Regiment.