Queen Elizabeth II spent the most terrifying 10 minutes of her life alone with an Irishman. At Buckingham Palace, in the early hours of July 9, 1982, she woke up to find an intruder called Michael Fagan standing at the end of her bed and dripping blood from a cut hand.
As frightened as she must have been, she managed to strike up a conversation about their children and kept him talking until help arrived.
When she lands in Dublin tomorrow for the first time, the queen will be hoping for a more relaxing Irish experience.
Whatever you think of her visit, it is certain to be a defining moment in the history of Anglo-Irish relations, particularly if she makes an official apology for British mistakes of the past. By the time she departs on Friday, however, the chances are that her private thoughts will be as much of a mystery as ever -- and that's exactly how she would want it.
Last week Elizabeth celebrated a personal milestone when she became the second-longest reigning monarch in British history (overtaking the unfortunate George III who famously lost the American colonies and then his mind).
The 85-year-old's excellent health means she has every chance of making it to September 2015 and even outlasting Queen Victoria. If she lives to 101, like the Queen Mother, Prince Charles will be pushing 80 and under huge pressure to pass the throne directly on to William and Kate.
Whoever succeeds Elizabeth will certainly have a hard act to follow.
Even British republicans tend to admit that she is a class act who has dedicated her entire life to preserving the dignity of the monarchy, often in very difficult circumstances.
While her husband and children have often made fools of themselves, she has been in the public eye since she was a small child and has barely put a foot wrong.
So what is she really like?
Winston Churchill met her when she was just two and thought she had "an air of authority astonishing in an infant". Helen Mirren portrayed her in The Queen as a decent but cold-hearted woman who never lets emotion interfere with her duties.
Tony Blair says he found her "quite shy" but terrifyingly direct in her manner of speech.
"Now let me tell you something, you don't get matey with the queen," Mr Blair wrote in his memoirs. "Occasionally she can be matey with you, but don't try to reciprocate or you get The Look.'"
We know that she loves horses, her corgi dogs (she once demoted a footman who gave them whiskey) and Scottish highland dancing. She supports Arsenal, follows Coronation Street and enjoys reading detective novels. She usually wears bright colours and hats because she wants to be visible in a crowd.
She never, ever gives personal interviews -- which means that although she must know tonnes of secrets about world leaders past and present, she is determined to take them with her to the grave. Elizabeth Windsor was not born to be queen. She spent the first 10 years of her life assuming, like everybody else, that her uncle Edward would assume the throne and then produce heirs of his own.
Her world was turned upside down in 1936 when Edward dramatically abdicated in order to marry the American divorcee Wallis Simpson, making his brother George king and Elizabeth the next in line.
As the Oscar-winning film The King's Speech showed, George VI was an insecure man with a strong sense of duty -- something he clearly passed on to his eldest daughter. On her 21st birthday she made a radio broadcast to the British Commonwealth in which she promised, "I declare before you all that my whole life, whether it be long or short, shall be devoted to your service."
During World War Two, Elizabeth trained as a military driver and mechanic (to this day, she is the only person in Britain allowed to drive without a licence or registration plate). Although some politicians wanted her to be evacuated to Canada, the royal family insisted on keeping her in the country. On the day that victory was declared, she and her sister Margaret mingled anonymously with the cheering crowds in London.
George VI died in 1952, apparently exhausted by the stress of his position. On the day of Elizabeth's coronation the following year, she received a good omen with the news that a British expedition had conquered Mount Everest for the first time. Millions of British families bought television sets to watch the ceremony, while in Ireland there were private screenings in parish halls for those afraid of offending republican sympathies.
Elizabeth first met Prince Philip of Greece when she was eight, fell in love with him five years later and married him at the age of 21 (in a dress that took 350 women seven weeks to make).
The union has produced four children and seems to be very happy, even if by his own admission he is seen as "a cantankerous old sod". His racially insensitive comments have often landed him in hot water, such as telling a group of British students in China, "If you stay here much longer, you'll go slit-eyed" and asking a Scottish driving instructor, "How do you keep the natives off the booze long enough to get them through the test?"
Elizabeth may not exactly be a touchy-feely person, but she has been known to get upset over her children's wayward love lives.
In 1992 the monarchy was rocked when Prince Charles separated from Diana, Princess Anne divorced Mark Phillips and Prince Andrew's wife Sarah was photographed topless while her financial adviser sucked her toes. At the end of the year, the queen gave an unusually personal speech in which she admitted it had been an "annus horribilis".
However, much worse was to come with the tragic death of Princess Diana (see panel ). During her reign, the queen has visited 129 countries but never once called in to see her nearest neighbours.
There has been some speculation that she is prejudiced against the Irish, particularly since her husband's uncle Lord Mountbatten was murdered by the IRA in Sligo in 1979.
Following that tragedy, Princess Margaret reportedly exclaimed, "The Irish are pigs!" -- although the Palace gamely insisted that she had actually said, "The Irish dance jigs."
Tomorrow afternoon, the Garden of Remembrance in Parnell Square will echo to the sound of God Save The Queen. The Irish authorities must be praying this does not turn out to be necessary.
Elizabeth II has waited a long time for this moment -- and the coming days should add yet another chapter to her remarkable life story.