For the Queen, 2012 promised to be an annus mirabilis
. Fresh off last year's royal wedding of Prince William
to Kate Middleton
, the Queen could anticipate her Diamond Jubilee followed by the Summer Olympics. Those games will draw worldwide attention to London.
But another recent event has drawn attention of a more sinister nature. And the murder mystery
unfolding at the Queen's Sandringham estate has cast a pall on the Windsor clan, royal experts say.
The royal family had just gathered for the holidays
at the sprawling estate when a roving dog walker made a gruesome discovery: the body of 17-year-old Alisa Dmitrijeva
, a Latvian immigrant and college student from nearby Wisbech, Cambridgeshire. She'd been missing since September and it took days to identify her
"It could have been one of them who stumbled on the body," one royal author tells PEOPLE. "The Queen must be very upset."
For more on the murder mystery at Sandringham, pick up the latest issue of PEOPLE, on newsstands Friday