Princess Catherine is celebrating her 44th birthday today, but long before she became the Princess of Wales, there was a moment in her relationship with Prince William that reportedly left her deeply shaken. The couple, now married for almost fifteen years, first met at university in the early 2000s. Their romance has since become one of the most closely followed royal love stories, yet like any long relationship, it has had moments of uncertainty behind the scenes.

According to royal author Katie Nicholl, one such moment came in 2008. That year, Prince William announced he would begin training as a full time pilot with the Royal Air Force Search and Rescue Force. Buckingham Palace confirmed he would start an eighteen month course in January 2009. If successful, he would go on to serve as an operational search and rescue pilot from 2010, with a typical tour lasting up to three years.