British honours are awarded on merit, for exceptional achievement or service.
The system is overseen by the Cabinet Office Honours and Appointments Secretariat, and British nationals or citizens of the 15 Commonwealth realms can be nominated.
The honours list consists of knights and dames, appointments to the Order of the British Empire and gallantry awards to servicemen and women, and civilians.
The Foreign Office has responsibility for the Diplomatic Service and Overseas List, which recognises service overseas, or service in the UK with a substantial international component. And honorary awards for foreign nationals are recommended by the foreign secretary.
Nominations, submitted either by government departments or members of the public, are divided into subject areas and assessed by committees of independent experts and senior civil servants.
Their assessments are passed to a selection committee that produces the list, independently of government, before it is submitted to the Queen through the prime minister.
The Queen informally approves the list and letters are sent to each nominee. Once a nominee accepts the proposed honour, the list is formally approved.
The honours are published in the official Crown newspaper, the London Gazette, twice a year - at new year, and in mid-June on the date of the Queen's official birthday.
The Central Chancery of the Orders of Knighthood at St James's Palace then arranges investitures for the recipients to be presented with their medals by the Queen or other members of the Royal Family.
Private nominations, made by individuals or by representatives of organisations to the Cabinet Office, traditionally make up about a quarter of all recommendations.
The honours list does not cover peerages. Since 2000, peers nominated by political parties have been vetted by the House of Lords Appointments Commission. The commission is also involved in making recommendations for non-party affiliated peerages.
An outgoing prime minister has the right to draw up a dissolution or resignation honours list on leaving office. The honours committees do not assess the list although it is submitted to the Cabinet Office for "probity and propriety checks". In the case of peerages, the House of Lords Appointments Commission vets the list.
A Parliamentary and Political Services Committee made up of a majority of independent members and the chief whips of the three major parties was set up in 2012 to consider honours for politicians and for political service.
In recent years, political donations made by a number of recipients have become the subject of particular scrutiny.
In a November 2011 response to a parliamentary committee's inquiry into the honours system, the Cabinet Office noted that all candidates for senior awards are "checked against the lists of donations maintained and made public by the Electoral Commission".
It added: "The Main Honours Committee must satisfy itself that a party political donation has not influenced the decision to award an honour in any way."
In the same year the Commons Public Administration Committee urged the government to review the way the honours system is administered, calling on ministers to set up independent bodies to nominate recipients for awards and decide when they should be withdrawn.
Forfeiting an honour
The Honours Forfeiture Committee considers cases where a recipient's actions "raise the question of whether they should be allowed to continue to be a holder of the honour".
The Queen's art adviser Anthony Blunt was stripped of his knighthood in 1979 after being revealed as a Soviet spy, and former Royal Bank of Scotland boss Fred Goodwin, who was heavily criticised over his role in the bank's near-collapse, had his knighthood removed in 2012. Entertainer Rolf Harris lost his CBE in March 2015 following his conviction for indecent assault.
Meanwhile, a list of 277 people who had turned down honours between 1951 and 1999, and who had since died, was made public by the Cabinet Office following a BBC Freedom of Information request. It included authors Roald Dahl, JG Ballard and Aldous Huxley, and the painters Francis Bacon, Lucien Freud and LS Lowry.
Others reported to have turned down an honour in more recent years include David Bowie, Nigella Lawson and comedy duo Dawn French and Jennifer Saunders.
Types of honours
Knights and Dames
The honour of knighthood comes from the days of medieval chivalry, as does the method used to confer the knighthood - the accolade, or the touch of a sword by the sovereign.
A knight is styled "Sir" and their wives "Lady".
Women receiving the honour are styled "Dame" but do not receive the accolade.
The honour is given for a pre-eminent contribution in any field of activity.
The rank of Knight Commander (KBE) or Dame Commander (DBE), Order of the British Empire, appears on the Diplomatic Service and Overseas list.
The Order of the Bath
The Order of the Bath is an order of chivalry and was founded in 1725 for service of the highest calibre. The order has a civil and military division and is awarded in the following ranks: Knight Grand Cross (GCB), Knight Commander (KCB) and Companion (CB).
The Order takes its name from the symbolic bathing which, in former times, was often part of the preparation of a candidate for knighthood.
Order of St Michael and St George
This Order was founded by King George III in 1818 and is awarded to British subjects who have rendered extraordinary and important services abroad or in the Commonwealth. Ranks in the Order are Knight or Dame Grand Cross (GCMG), Knight or Dame Commander (KCMG or DCMG) and Companion (CMG).
Order of the Companions Honour
This is awarded for service of conspicuous national importance and is limited to 65 people. Recipients are entitled to put the initials CH after their name.
Orders of the British Empire
King George V created these honours during World War One to reward services to the war effort by civilians at home and service personnel in support positions.
The ranks are Commander (CBE), Officer (OBE), and Member (MBE).
They are now awarded for prominent national or regional roles and to those making distinguished or notable contributions in their own specific areas of activity.
British Empire Medal
The medal was founded in 1917 and was awarded for "meritorious" actions by civilians or military personnel, although the recipients did not attend a royal investiture.
Scrapped in 1993 by former Conservative Prime Minister John Major, as part of his drive towards a "classless" society, the BEM was revived in 2012.
Royal Victorian Order
By 1896, prime ministers and governments had increased their influence over the distribution of awards and had gained almost total control of the system. Therefore, Queen Victoria instituted The Royal Victorian Order as a personal award for services performed on behalf of the Royal Family.
The ranks are Knight or Dame Grand Cross (GCVO), Knight or Dame Commander (KCVO or DCVO), Commander (CVO), Lieutenant (LVO) and Member (MVO).
Royal Victorian Medal
Associated with the Royal Victorian Order is the Royal Victorian Medal which has three grades: gold, silver and bronze. The circular medal is attached to the ribbon of the Order.
Royal Red Cross
Founded in 1883 by Queen Victoria, the award is confined to the nursing services. Those awarded the first class are designated "Members" (RRC): those awarded the Second Class are designated "Associates" (ARRC).
Queen's Police Medal
Awarded for distinguished service in the police force.
Queen's Fire Service Medal
Given to firefighters who have displayed conspicuous devotion to duty.
Queen's Ambulance Service Medal
Awarded for distinguished service in the ambulance service.