If Elizabeth II is still on the throne on Sept. 10, 2015, she’ll surpass Victoria as the longest-reigning monarch in British history.

Interestingly, no one knows precisely when she became queen. George VI died in his sleep sometime between 10:30 p.m. on Feb. 5, 1952, and 7:30 a.m. on Feb. 6. At that instant, Elizabeth acceded to the throne. At the time she was staying at the Treetops Hotel in Kenya; according to Ben Pimlott’s 1998 biography The Queen, at the moment of George’s death she was either asleep, eating breakfast, or watching the sun rise.

Mike Parker, a member of the royal party, had joined her at the top of the tree that morning to watch the dawn break over the jungle when he noticed an eagle hovering just over their heads and “for a moment, he was frightened that it would dive onto them.”

“I never thought about it until later,” he said, “but that was roughly the time when the king died.”