I'm not claiming to believe in Astrology, but rather am taking it for granted that Kings and Queens have historically planned their lives based on the guidance of their soothsayers.
To quote St. Thomas Aquinas
The celestial bodies are the cause of all that takes place in the sublunar world.From Gryphon Astrology:
The royal wedding horoscope is set for April 29, 2011, 11:00 am, British Summer Time, London, England. You might wonder whether this horoscope has been elected; I believe that it is a time set by an astrologer. In fact, I believe that Charles and Diana’s wedding was also astrologically elected. Looking at the horoscope for William and Kate’s wedding, I suspect that the astrologer was working with significant time constraints and was making the best of a challenging astrological configuration.
The horoscope is strongly configured to favor Prince William as much as possible, but is rather unfavorable for Kate. It may be that given the time constraints, the astrologer (presumably paid by the royal family) could only strengthen the significators of one party to the marriage, and that would be the prince. Kate’s happiness and well-being, whatever good personal characteristics she may have, is not nearly as important to the royal family as that of William.