Then Princess Elizabeth, the eldest daughter of the Duke and Duchess of York, was never expected to become Queen.
The life of Queen Elizabeth, who celebrated her 96th birthday on Thursday, changed in 1936 when her uncle, King Edward VIII abdicated, her father became King George VI and the young Princess became the heir presumptive.
Later, following the sad death of her father in 1952, Princess Elizabeth became Queen Elizabeth II aged just 25, and this year is celebrating 70 years on the throne – a first in British history.
Queen Elizabeth II turned 96 on Thursday, receiving a rousing “Happy Birthday” from a military band outside her Windsor Castle home, after a troubled year hit by health concerns.
No official engagements were planned, although royal officials released a photograph of the horse-loving head of state with two of her fell ponies.
Her grandson Prince William and his wife Kate called her “an inspiration to so many across the UK, the Commonwealth and the world”.
Royal tradition since the 18th century has also seen the monarch have a second, official birthday, typically celebrated in warmer weather in June.