The origins of knighthood are obscure, but they are said to date back to ancient Rome, where there was a knightly class of Ordo Equestris (an order of mounted nobles).  The Emperor Charlemagne had knights, and from him we have the orders of chivalry, from which the medieval knighthood grew, along with the system of heraldry.

Knighthood became an established military guild in many European countries, and it had certain characteristics: a would-be knight would undertake strict military training from boyhood, including some time as an assistant (an esquire, probably derived from the Latin scutifer; shield-bearer) to a knight with whom he rode to war.

He would also have to prove himself worthy according to rules of chivalrous behaviour, such as 'faithfulness to his Saviour and his Sovereign', generosity, self-denial, bravery and skill at arms.

In addition, he would be expected to have the financial ability to support the honour of knighthood, so that he could provide himself with arms, armour, horses and the required number of armed followers to render military service to his Sovereign for a minimum period each year.

In former times, no person could be born a knight (the use of the term 'knight' in England may have come from the Anglo-Saxon word cnyht or cnite, meaning 'military follower') - even monarchs and their heirs had to be made knights.

Alfred knighted his grandson Athelstan; William I was knighted when he became king (although he had previously been knighted in Normandy); Edward III, Henry VII and Edward VI were all knighted, after coming to the throne, by one of their subjects.

The conferment of knighthood involved strict religious rites (encouraged by bishops who saw the necessity of protecting the Church, and of emphasising Christian ideals in order to temper the knights' ferocity), which included fasting, a vigil, bathing, confession and absolution before the ceremony took place.

The first and simplest method of knighting was that used on battlefields, when the candidate knelt before the royal commander of the army and was 'stricken with the sword upon his back and shoulder' with some words such as 'Advances Chevalier au nom de Dieu'. (The action of touching the sword on the recipient's shoulder is known as dubbing.)

The second method involved greater ceremony, which could include the offering by the knight of his sword on the altar.

Although the monarch's 'lieutenants in the wars' and a few others of high birth 'possessed of special royal authority' could knight others, over the years successive Sovereigns began drastically to limit the power to confer knighthood - particularly Henry VIII.

Eventually, it became the custom for monarchs to confer all knighthoods personally, unless this was quite impracticable.

However, knighthoods were not necessarily sought after, as there were men who wanted to avoid an honour which compelled them (at great expense and personal inconvenience) to reinforce the Sovereign's armies.

The alternative to knighthood was the payment of a fine instead of military service, and kings such as Edward II, James I and Charles I found such fines a useful source of income for the crown (this practice of fining was abolished in Charles II's reign).

James I even instituted a new honour of baronetcy (a title which could be passed on to descendants) in 1611, so that he could raise money and valuable reinforcements for his army.

In extreme cases, when a knight was found guilty of treachery or treason, he could lose his honour by formal degradation - a public ceremony in which his accoutrements were taken off him.

In 1468, Sir Ralph Grey was taken to Doncaster where, being guilty of treason, his 'gold spurs were hewn from his heels while his sword and all his armour were broken'.

The last public degradation was in 1621 at Westminster Hall, when Sir Francis Mitchell was found guilty of 'grievous exactions' and had his spurs broken and thrown away, his belt cut and his sword broken over his head. Finally, he was pronounced to be 'no longer a Knight but Knave'.

Other more recent examples of degradation from honours are when Sir Roger Casement had his knighthood cancelled during the First World War for treason (he was subsequently executed), and in 1979 when Sir Anthony Blunt (a former Surveyor of The Queen's pictures) also had his knighthood withdrawn.

Currently, a person may be stripped of his knighthood should he be convicted of a criminal offence by a Court of Justice.

Today, The Queen (and occasionally members of the Royal Family on her behalf) confers knighthood in Britain. The knight-elect can be knighted at a public Investiture or privately.

The ceremony is similar: after his name is announced, the knight-elect kneels on a knighting-stool in front of The Queen who then lays the sword blade on the knight's right and then left shoulder.

After he has been dubbed, the new knight stands up (contrary to popular belief, the words 'Arise, Sir ---' are not used), and The Queen then invests the knight with the insignia of the Order to which he has been appointed (a star or badge, depending on the Order).

By tradition, clergy receiving a knighthood are not dubbed, as the use of a sword is thought inappropriate for their calling.

Over the centuries, knighthood has evolved: it is no longer awarded solely for military merit, it cannot be bought and it carries no military obligations to the Sovereign.

However, knighthood remains as a form of recognition for significant contributions to national life. Recipients today range from actors to scientists, and from school head teachers to industrialists.
 
Foreign citizens occasionally receive honorary knighthoods; they are not dubbed, and they do not use the style 'Sir'. Such knighthoods are conferred by The Queen, on the advice of the Foreign and Commonwealth Office, on those who have made an important contribution to relations between their country and Britain.

Foreign citizens with knighthoods include the former US Secretary of Defense Caspar Weinberger, Chancellor Kohl, President Mitterrand and Mayor Giuliani of New York.