Queen Elizabeth II, Britain's longest-serving monarch, turns 90 on Thursday 21 April 2016. She overtook her great-great-grandmother Queen Victoria's record time on the throne in September 2015, and is also the world's oldest reigning monarch.

Elizabeth Alexandra Mary was born at 2.40am at 17 Bruton Street, Mayfair, on 21 April 1926, during the reign of her grandfather, King George V. As a young princess, Elizabeth had not expected to become monarch as her father only took the crown when his elder brother, Edward VIII, abdicated in 1936 to marry American divorcee Wallis Simpson.

She was 25 when she ascended to the throne on 6 February 1952, following the sudden death of her father, King George VI, at the age of 56.

Queen 90th birthday
1926: Family portrait of the Duke and Duchess of York (later King George VI and Queen Elizabeth) with the newborn princess (later Queen Elizabeth II)Universal History Archive/UIG via Getty Images
Queen 90th birthday
1928: Princess Elizabeth, aged two, poses wearing a party dressThe Print Collector/Print Collector/Getty Images
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July 1936: Princess Elizabeth hugs a corgiLisa Sheridan/Studio Lisa/Getty Images
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12 October 1940: Princess Elizabeth makes her first radio broadcast, accompanied by her younger sister Princess MargaretGetty Images
Queen 90th birthday
8 July 1941: Princess Elizabeth and Princess Margaret Rose play with their pet chameleon in the grounds of Windsor CastleGetty Images
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23 December 1944: Princess Elizabeth appearing in a production of Old Mother Red Riding Boots, a royal family pantomimeLisa Sheridan/Studio Lisa/Getty Images
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18 April 1945: Princess Elizabeth changes the tyre of a vehicle as she trains as an ATS Officer during World War TwoCentral Press/Hulton Archive/Getty Images
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8 May 1945: (From left) Princess Elizabeth, Queen Elizabeth, prime minister Winston Churchill, King George VI and Princess Margaret Rose wave from the balcony of Buckingham Palace during VE Day celebrationsReg Speller/Getty Images
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9 July 1947: Princess Elizabeth, Philip Mountbatten, Queen Elizabeth (the future Queen Mother), King George VI and Princess Margaret pose in Buckingham Palace on the day the engagement of Princess Elizabeth and Philip Mountbatten was officially announcedAFP
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July 1947: Princess Elizabeth poses in the state apartments at Buckingham Palace upon her engagement to Prince PhilipHulton Archive/Getty Images
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20 November 1947: Princess Elizabeth and Prince Philip pose at Buckingham Palace after their wedding ceremony which was held at Westminster AbbeyTopical Press Agency/Getty Images
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14 December 1948: A Cecil Beaton portrait of Princess Elizabeth with her infant son Prince Charles (born on 14 November)Keystone-FranceGamma-Rapho via Getty Images
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circa 1950: A Cecil Beaton portrait of Princess Elizabeth in the drawing room of Clarence HouseBettmann Archive/Getty Images
Queen 90th birthday
circa 1952: Princess Elizabeth and and husband Philip hold their two children, Charles and AnneAFP
Queen 90th birthday
28 September 1952: Princess Elizabeth watches her son Prince Charles playing in his toy car at BalmoralLisa Sheridan/Studio Lisa/Getty Images
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8 February 1952: Queen Elizabeth II is greeted by Sir Winston Churchill, Clement Attlee, Anthony Eden and Frederick James Marquis as she returns from Kenya. She was proclaimed Sovereign of each of the Commonwealth Realms two days earlier, upon the death of her father King George VI. Princess Elizabeth heard the news of her father's death while staying at Treetops, a game lodge in KenyaAFP
queen Elizabeth II longest reign
8 February 1952: A ceremony is held in London for the proclamation of Queen Elizabeth II's accession to the throneAFP
queen Elizabeth II longest reign
2 June 1953: Queen Elizabeth II, accompanied by Prince Philip, waves to the crowd from the balcony at Buckingham Palace after being crowned at Westminster Abbey. Her coronation was the first worldwide televised eventAFP

The year she became queen, Winston Churchill was prime minister, Harry Truman was US president, Joseph Stalin was leader of the Soviet Union, the Korean War was raging and Britain announced it had the atom bomb. Since becoming queen, she has seen 12 prime ministers and 12 US presidents. She has witnessed the intensification and end of the Cold War and the rise and fall of the Berlin Wall.

queen Elizabeth II longest reign
16 May 1954: Queen Elizabeth II and her children Prince Charles and Princess Anne wave to the crowd from a balcony of Buckingham Palace after returning from a tripAFP
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2 February 1956: The Queen inspects men of the newly-renamed Queen's Own Nigeria Regiment, Royal West African Frontier Force, at Kaduna Airport, NigeriaFox Photos/Hulton Archive/Getty Images
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circa 1960: The Queen plays with her daughter Anne
Queen 90th birthday
25 January 1961: The Queen perches in a howdah on the back of an elephant in Benares, during her tour of IndiaHulton Archive/Getty Images
queen Elizabeth II longest reign
26 January 1961: The Queen and Prince Philip pose with the Maharaja and Maharani of Jaipur after a tiger shoot in Jaipur, IndiaAFP
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1965: The Queen and Prince Philip, with their children (left to right) Edward, Anne, Charles and Andrew, celebrate the Queen's 39th birthday at WindsorKeystone/Getty Images
Queen 90th birthday
30 July 1966: England captain Bobby Moore holds the Jules Rimet trophy aloft after receiving it from the Queen upon their 4 -2 victory over West Germany in the the World Cup final at Wembley StadiumFox Photos/Hulton Archive/Getty Images
queen Elizabeth II longest reign
11 July 1969: The Queen holds the hands of her 20-year-old son Charles during his investiture as Prince of Wales at Caernarfon CastleAFP
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April 1973: Prince Philip looks on as the Queen uses a camera at the Badminton Horse TrialsTim Graham/Getty Image
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1974: The Queen arrives at Aberdeen airport with her corgis to start her holidays in BalmoralAnwar Hussein/Getty Images
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April 1976: The Queen poses for a portrait on her 50th birthday, in WindsorAFP
queen Elizabeth II longest reign
February 1977: Queen Elizabeth II poses for a special Jubilee picture in the Throne Room of Buckingham Palace, after she had delivered the traditional Queen's speech at the 1976 official State Opening of Parliament. She wears the Imperial State Crown and the Robe of State. Around her neck is the Jubilee Necklace of diamonds and pearls and the chain is the Collar of the Order of the GarterAFP]
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7 June 1977: Queen Elizabeth ll greets the public during a Silver Jubilee walkaboutAnwar Hussein/Getty Images
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17 February 1979: Her Majesty wears a blue outfit with a turban-style hat and sapphire brooch during a visit to Riyadh in Saudi ArabiaTim Graham/Getty Images
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May 1979: The Queen, wearing a pink cape, attends the Royal Windsor Horse ShowTim Graham/Getty Images
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circa 1980: The Queen, wearing a green coat and matching hat, laughs as she attends the Royal Windsor Horse ShowTim Graham/Getty Images
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29 July 1981: Prince Charles and Princess Diana kiss on the balcony of Buckingham Palace after their wedding. They are surrounded by their bridesmaids and pageboys as well as Queen Elizabeth Il, Prince Edward and the Queen MotherTim Graham Photo Library/Getty Images
queen Elizabeth II longest reign
29 July 1981: Members of the British and European royal families surround Prince Charles and Princess Diana after their weddingAFP]
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4 August 1982: Princess Diana holds her son Prince William, while Prince Charles, Prince Philip, the Queen and the Queen Mother look on, at Buckingham Palace after William's christening ceremonyFox Photos/Getty Images
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18 September 1982: Prince Andrew talks to his mother as his father looks on, aboard the air carrier HMS Invincible, upon his return from the Falklands war, where he served as a helicopter pilotAFP]
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October 1982: The Queen and Prince Philip visit the Solomon Islands during a tour of the South PacificAnwar Hussein/Getty Images
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21 December 1984: The Queen and other members of the royal family laugh at the antics of young Prince William as his brother Harry is christened at Windsor CastleAnwar Hussein/Getty Image
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11 May 1985: The Queen applies lipstick as she waits for Prince Phillip to enter the ring with his horse team at the Windsor Horse ShowDavid Levenson/Getty Images
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23 July 1986: Prince Andrew and his bride Sarah Ferguson, the Duchess of York, wave to crowds from the balcony of Buckingham Palace while Queen Elizabeth II and the Queen Mother look onAFP]

The queen and the royals have endured some low points, particularly in the 90s, during the divorces of her sons Charles and Andrew and the subsequent death of Princess Diana. However, the popularity of the royals has rebounded with the marriage of Prince William to Kate Middleton and the arrival of their two children, Prince George — now third in line to the throne — and Princess Charlotte.

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5 September 1997: The Queen and Duke of Edinburgh look at the mass of floral tributes laid outside Buckingham Palace in memory of Diana, Princess of WalesReuters
queen Elizabeth II longest reign
1 January 2000: The Queen joins hands with the Duke of Edinburgh, Prime Minister Tony Blair and Cherie Blair to sing Auld Lang Syne at midnight during New Year's celebrations at the Millennium DomeReuters
queen Elizabeth II longest reign
11 July 2000 : The Queen Mother declines the hand of her grandson Prince Charles as she walks down the steps of St Paul's Cathedral following a service for her 100th birthday. They are accompanied by Queen Elizabeth II, the Duke of Edinburgh, Prince Andrew and Princes Harry and WilliamJonathan Evans/AFP
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4 August 2000: Queen Elizabeth the Queen Mother celebrates her 100th birthday from the balcony of Buckingham Palace with her daughter the QueenIan Waldie/Getty Images
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2 April 2002: The Queen rides her horse in the grounds of Windsor Castle, three days after the death of her motherDan Chung
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9 April 2002: Her Majesty walks behind her mother's coffin following the Queen Mother's funeral at Westminster Abbey in LondonDan Chung/Reuters
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4 June 2002: The Queen and the Duke of Edinburgh travel back to Buckingham Palace after the Golden Jubilee Service of Thanksgiving held at St Paul's Cathedral. Thousands of people gathered in central London for the festivities on the final day of the celebratory weekend marking the Queen's 50th year on the throneMurray Sanders/Pool
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14 January 2003: The Queen leaves King Edward VII hospital in London with a cane after undergoing surgery to remove torn cartilage from her right kneeIan Waldie/Getty Images
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23 November 2004: The Queen and Prince Philip arrive for the state opening of Parliament in LondonIan Waldie/Getty Images
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9 April 2005: The Prince of Wales and his new bride Camilla, Duchess of Cornwall, pose with Prince Harry, Prince William, Tom and Laura Parker Bowles, the Duke of Edinburgh, the Queen and Camilla's father Major Bruce Shand, in the White Drawing Room at Windsor Castle after their wedding ceremonyHugo Burnand/Pool
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14 May 2005: The Queen is reflected in the wing mirror of her Land Rover as she follows The Duke of Edinburgh as he competes in the Driving Grand Prix Competition at the Royal Windsor Horse ShowJulian Finney/Getty Images
queen Elizabeth II longest reign
12 April 2006: The Queen and Prince Harry smile during the Sovereign's Parade at the Royal Military Academy in SandhurstDylan Martinez/Reuters
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15 December 2006: The Queen looks up at a smiling Prince William during the Sovereign's Parade at the Royal Military Academy in SandhurstDylan Martinez/Reuters
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22 November 2006: The Queen receives a scroll from Bruce Two Dogs Bozsum, chairman of the Mohegan Tribal Council, at Southwark Cathedral in LondonStefan Rousseau
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19 November 2007: The Queen and the Duke of Edinburgh walk at Broadlands in Romsey, southern England, as they prepare to celebrate their diamond wedding anniversaryFiona Hanson/Pool
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18 November 2009: Queen Elizabeth II leaves the Houses of Parliament after delivering her speechToby Melville/Reuters
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7 December 2009: The Queen meets Lady Gaga following the Royal Variety Performance in BlackpoolLeon Neal/AFP
queen Elizabeth II longest reign
17 December 2009: The Queen boards a scheduled train at Kings Cross station in London to go to Kings Lynn in Norfolk for ChristmasStefan Rousseau/Pool
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27 April 2010: The Queen leaves Cymru Arena in Llandudno during a visit to North WalesChris Jackson/Getty Images
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1 April 2011: The Queen arrives to visit her grandson, Prince William, at RAF Valley on Anglesey in north Wales, on a windy dayPhil Noble/Reuters
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29 April 2011: Newly-weds Prince William and Kate Middleton kiss on the balcony at Buckingham Palace, watched by members of the royal familyPaul Gilham/Getty Images
queen Elizabeth II longest reign
24 May 2011: The Queen holds onto her hat in the wind as she speaks with US President Barack Obama at Buckingham Palace, during his two-day state visitMurray Sanders/Pool
queen Elizabeth II longest reign
3 June 2012: The Queen waves to the crowds from the Spirit of Chartwell during the Diamond Jubilee River Pageant on the River Thames. She is accompanied by Prince Philip, Camilla and Kate Middleton in a gilded royal barge leading an armada of 1,000 boatsJohn Stillwell/Pool
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13 June 2012: Kate Middleton laughs as the Queen gestures while they watch part of a children's sports event during a visit to Vernon Park in NottinghamPhil Noble/Reuters
queen Elizabeth II longest reign
24 July 2012: Her Majesty the Queen poses for a photograph with Prime Minister David Cameron and former Prime Ministers John Major, Tony Blair and Gordon Brown at 10 Downing Street where they had lunch to mark the Queen's Diamond Jubilee.Stefan Rousseau/Pool
queen Elizabeth II longest reign
1 September 2012: Prince Philip, the Queen and Prince Charles cheer as competitors participate in a sack race at the Braemar Gathering in ScotlandRussell Cheyne/Reuters
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20 June 2013: The Queen celebrates with members of her family and her racing team as her horse Estimate wins The Gold Cup at Royal AscotDarren Staples/Reuters
queen Elizabeth II longest reign
23 October 2013: The Queen looks on as Prince William and Kate Middleton carry Prince George for his christening at St James's Palace in LondonJohn Stillwell/Pool
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11 April 2014: The Queen reacts as Irish President Michael D Higgins and his wife Sabina prepare to leave Windsor Castle. Higgins was the first Irish president to make a state visit to Britain since independenceLeon Neal/AFP
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24 June 2014: A youth takes a selfie in front of the Queen during her visit to St George's indoor market in Belfast, Northern IrelandPeter Macdiarmid/Getty Images
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17 July 2014: The Queen meets construction workers as she attends the official opening of the refurbished Reading StationBen Gurr/Reuters
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16 October 2014: The Queen walks through a field of ceramic poppies that form part of "Blood Swept Lands and Seas of Red" at the Tower of London, an installation commemorating the centenary of World War ILuke MacGregor/Reuters
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4 June 2015: The Countess of Wessex, Princess Anne and members of the Women's Institute look on as the Queen cuts a cake celebrating the organisation's centenary at the Royal Albert Hall in LondonChris Jackson/Getty Images
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18 May 2015: The Queen greets Prince Harry at the annual Chelsea Flower show in LondonJulian Simmonds
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27 May 2015: Queen Elizabeth II, accompanied by the Duke of Edinburgh and followed by the Prince of Wales and the Duchess of Cornwall, passes through the Royal Gallery during the State Opening of ParliamentGeoff Pugh
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13 June 2015: The Queen is accompanied by Camilla, Prince Charles, Prince William (holding Prince George), Kate Middleton and Prince Andrew on the balcony at Buckingham Palace after the Trooping the Colour ceremony at Horse Guards Parade to honour the Queen's official birthdayStefan Wermuth/Reuters
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24 June 2015: Queen Elizabeth II attends a banquet in Berlin during her four-day State Visit to GermanyMichael Ukas
queen Elizabeth II longest reign
5 July 2015: Prince William and Kate Middleton talk to the Queen, Prince Phillip and Camilla as they arrive at the Church of St Mary Magdalene on the Sandringham Estate for the christening of Princess CharlotteChris Jackson/Getty Images
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5 July 2015: Prince George talks to the Queen outside the Church of St Mary Magdalene on the Sandringham Estate for the christening of Princess CharlotteChris Jackson/Getty Images
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9 September 2015: The Queen travels on a steam train to inaugurate the new Scottish Borders Railway on the day she became Britain's longest reigning monarchAndrew Milligan
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5 November 2015: The Queen looks at a display of medals during a visit to Imjin barracks in Innsworth, GloucestershireRichard Pohle
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19 November 2015: The Queen is given a tour of a tram on the Metroline Tramline Extension in BirminghamChris Radburn
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25 December 2015: The Queen attends a Christmas Day church service at SandringhamChris Jackson/Getty Images
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23 February 2016: The Queen attends the formal unveiling of the new logo for Crossrail, which is to be named the Elizabeth line in her honour, at the construction site of Bond Street stationRichard Pohle
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8 March 2016: The Queen smiles as she meets people being helped by the Prince's Trust at the Prince's Trust Centre in Kennington, LondonChris Jackson/Getty Images
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Prince Charles, the Queen, Prince George and Prince William pose in the White Drawing Room at Buckingham Palace for a Royal Mail stamp sheet to mark her 90th birthdayRanald Mackechnie/Royal Mail/Getty Images
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20 April 2016: The Queen poses in the private grounds of Windsor Castle on the steps at the rear of the East Terrace and East Garden with four of her dogs: clockwise from top left Willow (corgi), Vulcan (dorgie), Candy (dorgie) and Holly (corgi)Annie Leibovitz via Getty Images
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20 April 2016: Her Majesty with her five great-grandchildren and her two youngest grandchildren in the Green Drawing Room at Windsor Castle. The children are: James, Viscount Severn (left), 8, and Lady Louise (second left), 12, the children of The Earl and Countess of Wessex; Mia Tindall (holding the Queen's handbag), the two year-old-daughter of Zara and Mike Tindall; Savannah (third right), 5, and Isla Phillips (right), 3, daughters of The Queen's eldest grandson Peter Phillips and his wife Autumn; Prince George (second right), 2, and in The Queen's arms and in the tradition of Royal portraiture, the youngest great-grandchild, Princess Charlotte (11 months)Annie Leibovitz via Getty Images

The Queen will spend her actual birthday in Windsor, where she will meet and greet members of the public in a short walkabout near the castle. Her official birthday day will be marked in June, with a service of thanksgiving at Westminster Abbey, the Trooping The Colour parade and a giant street party on the Mall in front of Buckingham Palace for representatives of all the charities the Queen supports.