How much do we actually know about 28-year-old His Royal Highness Prince William Arthur Philip Louis of Wales, Royal Knight Companion of the Most Noble Order of the Garter ?
Of course, we know the biographical highlights: that he earned a Master of Arts degree from Scotland's University of St. Andrews (upper second class honours in geography); that he's a flight lieutenant and fully certified helicopter pilot, now attached to the RAF Valley Search and Rescue Training Unit; that he lives at Clarence House on the Mall, the official home of his father, Charles, the Prince of Wales, and that he's a fiercely competitive athlete - a professional polo player and, while at college, played water polo on the Scottish national team at the Celtic Nations tournament in 2004.
About the young man himself, second in line after his father to the throne - his core character, what his fundamental values are - we have as yet only a few clues.
Those clues we do have, however, are instructive.
Impulsive, surely, he is not. After all, it took a courtship of eight years for him to propose to Kate Middleton, who was among his flatmates during his years at St. Andrew's. Life decisions, no less than monarchical ones, ought not to be rash.
That he has chosen a commoner for a marital partner speaks volumes. It bespeaks strength, needed to overcome Buckingham Palace's opposition which, at some level, was almost certainly voiced. And it bespeaks an independent spirit, not dissimilar to the one that was often said to characterize his late mother, Diana, Princess of Wales.
Indeed, more than most members of the Royal Family, and despite an upbringing of pomp and privilege, Prince William appears to have a genuine feel for the common man. That, too, may be a maternal legacy.
He spent part of his so-called gap year - after graduating from Eton College and before starting university - in Belize and Chile, living and working among the hoi-polloi and, more than once, scrubbing communal toilets and kitchen floors. At St Andrews, he shared shopping and laundry responsibilities, and could often be seen pedalling around the seaside town on his bike. In London, he volunteers his time for a charity that aids the homeless.
We know, too, that he has inherited his father's dry sense of humour. Asked some years ago about being considered the world's most eligible bachelor, pursued by women at every turn, he quipped, "I've never been aware of anyone chasing me, but if there were, could they please leave their phone number?"
His avowed love of Africa - he calls it "his second home" - seems entirely genuine, not simply another obligatory item to be added to the résumé of the man who might be king. He's made several visits there, and is patron of the Tusk Trust , a 20-year-old charity involved in wildlife conservation, community development and education across the continent.
In a statement issued in June, on the eve of the FIFA World Cup, he cited not only the rapid socio-economic change that Africa is experiencing, but referenced "another Africa: the vast, timeless expanses - indescribably beautiful, but also rife with great challenges for humanity and the natural world."
And it is surely no accident that, last October, during a 10-day safari, Prince William chose a remote mountaintop in Kenya, to propose formally to Ms. Middleton. As he said at Tuesday's official announcement. "I had been planning it for a while. It really felt right in Africa. I had done some planning to show my romantic side."
Romantic, but also acutely aware of symbolism. It was his own mother's engagement ring, given to her by Prince Charles all those years ago, that Prince William chose to slip onto the finger of his betrothed. "I was carrying the ring around for three weeks in a rucksack before that. And I literally would not let it go, wherever I went."
In a way, he's been carrying it much longer than that, since her tragic death 13 years ago. One can only guess at the strength of the emotional bond that connected Prince William to Princess Diana. He might well have given any ring to Miss Middleton. With this one, it is clear, he has also given his heart.