She has lived longer than any of her predecessors, seen a dozen prime ministers come and go and presided over six decades of British history - from postwar recovery to the death of Princess Diana and terror attacks on London.

Now Queen Elizabeth II is set to become the longest reigning monarch in British history. On Wednesday, she beats the record set by her great-great-grandmother Queen Victoria - 63 years and 7 months - more than a century ago. Only four other British kings and queens have reigned 50 years or more.

"You have to be a certain age to remember a time when she wasn't the queen," said royal historian and commentator Hugo Vickers.