Incorporated by royal charter in 1537 by King Henry VIII, it is the oldest regiment in the British Army and is considered the second-oldest military unit in the world.

The HAC can trace its history back as far as 1087,[9] but it received a royal charter from Henry VIII on 25 August 1537, when Letters Patent were received by the Overseers of the Fraternity or Guild of St George authorising them to establish a perpetual corporation for the defence of the realm to be known as the Fraternity or Guild of Artillery of Longbows, Crossbows and Handgonnes.

[17] In 1638, Sir Maurice Abbot granted the Company use of lands at its current site south of Bunhill Fields Burial Ground on City Road, which in 1649 consisted of twelve acres enclosed by a brick wall and pale.

[19] On 28 October 1664, in the New Artillery Gardens, the body of men that would become the Royal Marines was first formed with an initial strength of 1,200 infantrymen recruited from the London Trained Bands as part of the mobilisation for the Second Anglo-Dutch War.

[20][21] The Company served in Broadgate during the Gordon Riots of 1780[22] and in gratitude for its role in restoring order to the city, the Corporation of London presented "two brass field-pieces", which led to the creation of an HAC Artillery Division.

Second Lieutenants Reginald Leonard Haine and Alfred Oliver Pollard, of the 1st Battalion HAC, were awarded Victoria Crosses for their actions at Gavrelle in 1917.

In the Battle of Vittorio Veneto, in October 1918, they led a force of Italians, Americans and British that compelled the garrison of the strategic island of Papadopoli (in the main channel of the River Piave) to surrender.

In the German counter-attack during the Second action of Es Salt on 1 May 1918, A Battery was forced to make a rapid withdrawal under heavy fire, which resulted in the loss of all its guns.

[40][41] In 1919, Lieutenant-Colonel Edward Lisle Strutt, arranged for a detachment of the 2nd Battalion to form a Guard of Honour at Imst Station to give a final Royal Salute on the departure of the Imperial State Train for Charles I, the last Austro-Hungarian Emperor-King, to safety in Switzerland, after having served as the family's protector at Eckartsau on the personal initiative of King George V.[42][43] When the Territorial Force was reconstituted as the Territorial Army (TA) in 1920, the HAC infantry battalion was reformed, while A and B Batteries formed a composite RHA unit with the City of London Yeomanry (Rough Riders) (one battery) as 11th (HAC and City of London Yeomanry) Brigade, RHA.

[49] The 12th (HAC) Regiment RHA took part in the Operation Torch landings and were in action at Thala in February 1943, where they halted a German advance following the Battle of the Kasserine Pass.

[50] The 13th (HAC) Regiment RHA equipped with Sexton self-propelled guns fought in Normandy, the Netherlands and across the Rhine into Germany as part of 11th Armoured Division.

[52] Anti-Aircraft Command mobilised on 24 August 1939, and so 86th (HAC) HAA Rgt was already manning static gunsites at places like Primrose Hill and Finsbury Park when war was declared on 3 September.

[63][64] In 1996, the first formed unit of the Regiment to be mobilised for active service since the Second World War was called up for Operation Resolute with the NATO IFOR in Bosnia and Herzegovina.

[88][89] The Regiment has had individuals or sub-units on active service at all times since 1996; with the personnel serving in a wide variety of roles in Northern Ireland, Bosnia, Kosovo, Iraq, Afghanistan and various countries in Africa.

[65] Commitments included the deployment of individuals to human intelligence roles in the Balkans (including as part of Joint Commission Observer teams) and then formed patrols to Bosnia, Kosovo and Iraq; independent sub-units to Operation Telic 4 and 5 in Iraq and L Troop to Operation Telic 9; as well as individual and group reinforcements to other infantry and artillery units.

[90] In Afghanistan deployed personnel were divided between operating and maintaining counter indirect fire systems and other high technology equipment and forming part of the Brigade Reconnaissance Force (BRF).

[91] On Tuesday 4 December 2007, Trooper Jack Sadler, who was serving with the BRF, was killed when his vehicle was hit by a blast north of Sangin, in Helmand Province.

[92] In 2008, the Runner-up for the Cobra Trophy for Volunteer Reservist of the year was Trooper Adam Cocks of 2 Squadron, who was severely injured in Afghanistan when his vehicle struck a mine.

The latter is similar to that of the Royal Artillery but with "HAC" and "Arma Pacis Fulcra" replacing "Ubique" and "Quo Fas et Gloria Ducunt".

Officers' crowns and stars are of the same pattern as those of the Grenadiers (Order of the Garter), woven for combat uniforms but in silver for Service and Barrack Dress.

The ribbon, based on The King's personal colours (in turn taken from the Royal Standard), is red and blue edged with narrow yellow stripes.

[107] In 1919, following a decision to increase the strength of the Metropolitan Police Reserve Force, the Home Secretary approached the HAC to form a Division of Special Constabulary.

[108] Following reorganisation, the Detachment is now part of the City of London Police Special Constabulary,[109] its administrative base is Armoury House.

[110] In 2010, the Ferrers Trophy was awarded to Special Constable Patrick Rarden of the detachment for using his banking skills and experience to help train colleagues and provide invaluable assistance to solve fraud cases.

[111] As well as the Army Reserve Regiment and Specials (the "Active Units"), the HAC exists as a separate charitable organisation[112]—often colloquially referred to as "The Company" or "The House".

The Company owns Armoury House and the regiment's current grounds and, in addition to supporting the Active Unit, provides the basis for a social calendar.

[119] From 1538 to 1658, the HAC occupied and trained at the Old Artillery Ground in Spitalfields on the site of the outer precinct of the dissolved Priory and Hospital of St Mary Spital.

It was built to replace a smaller 17th-century armoury; the central portion being completed in 1735 to designs by Thomas Stibbs financed in part by a gift of £500 from King George I. Subscriptions were received from members of the company and from the Court of Lieutenancy for the City of London.

An extension, faced in striped stone and granite, linking Finsbury Barracks to Armoury House was designed by Arnold & Boston and added in 1994.

The historic estate lies in the heart of the Brecon Beacons National Park and comprises approximately 14,000 acres (57 km2) of hill land.