right|thumb|100px|A ceremonial mace (English, 17th century) as carried by the monarch's sergeants-at-arms on state occasions.
A serjeant-at-arms or sergeant-at-arms is an officer appointed by a deliberative body, usually a legislature, to keep order during its meetings. The word "serjeant" is derived from the Latin , which means "servant".
In the Middle Ages, the serjeants-at-arms were bodies of armed men retained by the French and English monarchs: the ceremonial maces with which they are associated were originally a type of weapon. Serjeants-at-arms continue to serve a ceremonial role in the Royal Household of the United Kingdom; as such they represent the oldest royal bodyguard in England.
Origins
thumb|left|upright|French serjeants-at-arms in courtly (left) and military (right) dress (from a 14th-century [[bas relief, Couvent Sainte-Catherine-du-Val-des-Écoliers, Paris).]]
The most familiar use of the term "sergeant" today is as a military rank. In the medieval period, the soldier sergeant was a man of what would now be thought of as the 'middle class', fulfilling a junior role to the knight in the medieval hierarchy. Sergeants could fight either as heavy to light cavalry, or as well-trained professional infantry, either spearmen or crossbowmen. Most notable medieval mercenaries fell into the 'sergeant' class, such as Flemish crossbowmen and spearmen, who were seen as reliable quality troops. The sergeant class were deemed to be 'worth half of a knight' in military value.
As 'knight' came to signify social (rather than military) rank, so 'serjeant' began to be used for a particular social class (below that of a knight but above that of a gentleman; though by the end of the 14th century 'esquire' had displaced 'serjeant' to describe this class of people). (The usage has survived to this day in a few Household offices such as the Serjeant Surgeon and Serjeant of the Vestry).
The particular office of serjeant-at-arms originated in twelfth-century France, when King Philip II formed for himself a bodyguard of nobles and armed them with maces. The had a courtly as well as a military character, and their maces served both as an insignia of office and as a practical weapon: at court they wore robes, in the field they wore armour; either way they carried their maces. They were powerful figures, answerable to no judicial authority but the King and the Constable of France. It is from this body of men that the present-day serjeants-at-arms evolved.
History of the office in England
thumb|Two Serjeants-at-arms of the Royal Household escort the officers carrying the [[regalia into the Palace of Westminster for the State Opening of Parliament in 2022.]]
The earliest record of the Sergeants-at-Arms in England is found in 1278, when King Edward I formed them into a twenty-strong Corps to serve as a close escort.
Duties
In 1417 the King's brother, Thomas of Lancaster, published a set of instructions for the kings of arms, heralds and serjeants-at arms (among whom there had been a dispute about their places in processions). He reiterated the purpose of the serjeants-at-arms, "which were principally founded and ordained for the conservation of the person of the King and his Lords", and also described their appearance: "the Serjeants at Arms in Service Royal ought to stand before the King in such fashion attired: that is to say his head bare and all his body armed to the feet with arms of a Knight riding, wearing a gold chain with a medal bearing all the King's Coats" and with a "Mace of silver in his right hand, and in his left hand a truncheon". Under the Tudors the size of the corps was again increased; in 1492 they were summoned by King Henry VII to accompany him on a military venture in France. Elizabeth I maintained a body of twenty-five serjeants-at-arms; under her successor James I their number was reduced to sixteen. When a new serjeant-at-arms was created a ceremony was held in the Presence Chamber: the new officer knelt before the king, who invested him first with a collar of esses and then with the mace, before declaring "Rise up, Serjeant at Arms, and Esquire for ever". They continued to wait quarterly, in pairs, attending in the Presence Chamber on Sundays and festival days. On rare occasions (most notably coronations) all eight would be on duty: they would customarily go ahead of the King in pairs, escorting those carrying the items of regalia. At the coronation banquet they escorted the Lord High Steward and other Lords who walked ahead of the dishes of hot meat as they were brought to the newly-crowned King; and a pair of serjeants escorted the King's Champion at his entry into the hall.
In subsequent reigns their number was gradually reduced: to six under Edward VII, to four under George V, and three under Elizabeth II. At the coronation of Charles III two serjeants-at-arms walked in the procession ahead of the regalia: Paul Whybrew and Richard Thompson.
The original responsibilities of the sergeant-at-arms included "collecting loans and, impressing men and ships, serving on local administration and in all sorts of ways interfering with local administration and justice."
Parliamentary role
<!--In the UK Parliament, the format used in the House of Lords is 'Serjeant-at-Arms' (with hyphens), while in the House of Commons it is 'Serjeant at Arms' (without hyphens); this usage is followed in the section below.-->
thumb|right|upright|[[David Erskine (serjeant-at-arms)|David Erskine, House of Commons Serjeant at Arms (photo by J. B. Stone, 1906).]]
From an early time, individual serjeants-at-arms of the Royal Household were attached to certain Great Officers of State. The Lord High Steward had a serjeant-at-arms, as did the Lord High Chancellor and the Lord High Treasurer. The Lord Chancellor is still attended by a serjeant-at-arms on ceremonial occasions (unless the monarch himself is present).
The Lord Chancellor was ex officio speaker of the House of Lords (an arrangement that pertained until 2006). His designated serjeant-at-arms had an authorized deputy who was "in constant attendance upon the Great Seal". The duty of the serjeant (or his deputy), "besides that of bearing the gilt mace before the Lord Chancellor, Lord Keeper or Lords Commissioners in going or returning from Court or Parliament", was (on behalf of the Court of Chancery) "to execute all warrants against persons who have stood out commissions of rebellion" and to take them into custody.
In 1415, the King appointed one of his serjeants-at-arms (Nicholas Maudit) to the House of Commons; the appointment was at the Commons' request, as recorded in the Letters Patent.