Queen Elizabeth II, who celebrates her 90th birthday this week, is Britain's longest-serving monarch. In the public eye all her life, she rarely, if ever, expresses an opinion in public, and does not give media interviews. But previously published reports have given us some insight into the Queen's private life. The following facts may help reveal some of her personal history behind the closed palace doors.

Britain's Queen Elizabeth leaves the Houses of Parliament after delivering her speech in London, in this November 18, 2009 file photo. [Photo/Agencies]

Longevity

Many people are impressed by the Queen's longevity as the UK celebrates the 90th birthday of its longest-serving monarch. She has reigned for 64 years, last year overtaking her great-great-grandmother Queen Victoria. She has seen 12 prime ministers serve her, from Britain's great wartime leader Sir Winston Churchill through to the incumbent, David Cameron.