Video report by Mary Nightingale, ITV News Presenter
The Queen has the most recognisable face in the world and a "twinkle in her eye", fashion and portrait photographer David Bailey told ITV News.
Her Majesty today becomes the longest serving monarch in British history, overtaking the record previously held by her great-grandmother Queen Victoria.
Bailey, who has snapped the likes of Diana, Princess of Wales; Mick Jagger; the Beatles and Naomi Campbell, photographed Queen Elizabeth II last year for her official 88th birthday.
Speaking about spending the morning photographing the Queen at Buckingham Palace last year, Bailey said:
We laughed all morning with her.