Queen Elizabeth saw Prince Philip's death coming, says source

Queen Elizabeth was well-prepared for the tragic demise of her husband of 73 years, Prince Philip.

The Duke of Edinburgh, who was longest-serving consort to a ruling British monarch, died peacefully on Friday morning, the Buckingham Palace announced in a statement. 

According to Charles Anson, former press secretary to the Queen, the 94-year-old monarch was prepared for Philip's death after years of battling major health woes.

"She would have thought about this moment several times, and her way would be to remain as steady and as calm as possible," Anson told PEOPLE. "That comes naturally to her through her temperament and her experience."

Anson added, "In my years of working for her she was always calm, no matter what was going on. But for any human being, this is a very cathartic moment."

The royal insider added how Philip, after marrying the Queen, immediately became her rock throughout the years. 

"There were some things they had to deal with together that were difficult, but it was a long marriage with a great deal of happiness," Anson shared. "He took very seriously his role as a support for the Queen as monarch."

Philip was able to provide "a great level support from a strong outward-looking man of action that he was. He was a natural of his generation to be at his wife's side. He very quickly came to terms to watching to be in that role of support as well as running his own life."

Anson further said the Queen will be surrounded by her close family in the household in days to follow.

"She has an enormous amount of family support for her and will also take comfort from the enormity of the support from all over the world," he said.