Queen Elizabeth II, who on Monday marks exactly 60 years on the throne, has spent a lifetime upholding her pledges to serve her peoples, earning a reputation in the process for calm shrewdness.

When she ascended to the throne in 1952 aged just 25, Winston Churchill was prime minister of Britain, Jawaharlal Nehru led the newly-independent India and swathes of Africa and Asia were still governed by Britain.

In the 60 years since, Queen Elizabeth has been a symbol of constancy as Britain's empire dwindled, throughout the Cold War and through the huge social upheavals between the post-war gloom and the digital age.

Despite the changing times and the very public ups and downs of the royal family, Elizabeth remains a largely revered figure and can lay claim to be the most recognised woman on the planet.

Born in London on April 21, 1926, Elizabeth Alexandra Mary -- nicknamed 'Lilibet' by her family -- was third in line to the throne behind her uncle Edward, prince of Wales, and her father, George, duke of York.

But the princess became the heir after her uncle abdicated as King Edward VIII in 1936 to marry American divorcee Wallis Simpson, and her father succeeded as King George VI.

She was brought up by governesses, and moved into Buckingham Palace in 1937 when her father was crowned king. Towards the end of World War II, aged 18, she undertook national service and qualified as a military driver.

In 1947, she married her third cousin, naval commander Philip Mountbatten, who renounced his titles as a prince of Greece and Denmark to wed.

The couple's first son, Prince Charles, was born in 1948, followed by Princess Anne in 1950, Prince Andrew in 1960 and Prince Edward in 1964.

Elizabeth was visiting Kenya when her father suddenly died overnight in February 1952. She had been staying in the Treetops Hotel, famously going to sleep a princess and waking up a queen.

Her husband broke the news and she returned to Britain immediately.

She was crowned on June 2, 1953, becoming the 40th monarch since king William I in 1066.

She has been head of state of 32 realms, a figure now standing at 16 including Britain.

Although instantly recognizable in public with her trademark matching bright outfits and hats, the queen's private life remains somewhat an enigma.

She is an avid follower of horse racing and famously a lover of Corgi dogs, which she keeps as pets.

Her duties have kept her busy -- she has toured the world, visiting every Commonwealth country, while at home she fulfills hundreds of official engagements each year, from garden parties to hospital openings and state banquets.

The punishing schedule has been helped by her generally robust health, and the support of her husband Prince Philip.

Behind the scenes, she only ever takes Christmas Day off from the red boxes of official state papers that she has to plough through.

She has seen 12 different British prime ministers from Churchill through to David Cameron. Many have attested to her level-headed wisdom and thorough grasp of affairs.

Her devotion to duty has sometimes been misinterpreted as coldness -- most famously following the death of Diana, princess of Wales in a car crash in Paris.

But many see a queen who has shown throughout her life that she can adapt to the times with dignity.