Mark Cuthbert/UK Press/ABACAUSA

Wow! Those royals sure know how to keep a secret. While the world was busy wondering when Prince William and Kate Middleton were going to get engaged, turns out they already were! The prince proposed to Kate with the ring that belonged to his mother, the late Princess Diana, during their vacation in Kenya last month, before their rare public appearance together at a friends’ wedding (left)—the very one that put the engagement speculation into overdrive. Queen Elizabeth II has given her blessing as have Kate’s parents—Prince William asked her father for her hand in marriage. The wedding is set to take place in the spring or summer of 2011.

MORE! See the engagement rings of other royals.

View Kate Middleton’s spot-on-princess style.