The Queen is now the oldest monarch in the world after the death of 90-year-old King Abdullah of Saudi Arabia this morning.
The British monarch holds the distinction at the age of 88.
Elizabeth II, who became Queen in February 1952 following the death of her father, George VI, is older than Sultan Abdul Halim Mu'adzam Shah of Malaysia and Thailand's King Bhumibol Adulyadej, who are both 87.
The Queen will turn 89 on 21st April, having celebrated her Diamond Jubilee in 2012.
While her long-haul visits have been significantly scaled back in recent years, the Queen maintains a busy diary of public and private domestic engagements.
She is the second-longest reigning monarch in 1,000 years of British history, behind her great-great grandmother Queen Victoria, whose record she is due to surpass in September 2015.
Below are the five oldest monarchs in the world:
Queen Elizabeth II, born April 1926
Sultan Abdul Halim Mu'adzam Shah, born November 1927
King Bhumibol Adulyadej, born December 1927
King King Sabah Al-Ahmad Al-Jaber Al-Sabah, born June 1929
King Sheikh Humaid bin Rashid al-Nuaimi, born 1931