The hundred citizens, including the Queen, who are nearly octogenarians - her and her guests' eightieth birthdays don't actually fall till Friday - will gather for drinks in the picture gallery at Buckingham Palace followed by a lunch there together. On Friday, the Queen will have a less formal family dinner and a walk-about in front of crowds at Windsor Castle near London.
The celebrations are prompting reflection on Britain's system of constitutional monarchy where real power is wielded by elected politicians but a monarch who inherits the role is formally head of state.
Scandal and publicity have altered the role in recent years, shining an unforgiving light on what was for centuries a mystical, remote position. Despite the changes, there is no obvious appetite in Britain for any other form of government.
octogenarians
people from 80 to 89 years old ('octo' is Latin for 'eight')
fall
begin, happen (used only for dates)
are prompting reflection
are making people think
wielded
held and exerted (often used with the word 'power')
inherits
receives from her parents when they die
Scandal
general public outrage because of someone's behaviour
altered
changed
shining an unforgiving light on
exposing
mystical
mysterious, spiritually symbolic
appetite
desire, want
