According to sources this decision was made by leaders during a retreat at Windsor Castle on Friday afternoon. Meanwhile Commonwealth leaders said in a statement that "They recognize the role of the queen in championing the Commonwealth and its peoples and the next head of the Commonwealth shall be His Royal Highness Prince Charles, the Prince of Wales."
Meanwhile this decision comes after the 91 year old monarch made a personal request for her son to succeed her at the Commonwealth Heads of Government Meeting. Moreover the moments before she spoke, Prince Charles made an informal pitch to take over leading the group of 53 nations, offering a small reminder of his commitment to the Commonwealth.
He said "For his part, the Commonwealth has been a fundamental
feature of his life for as long as he can remember". Accordingly Canadian
Prime Minister Justin Trudeau had said he agreed "very much" with the
Queen's wishes and Maltese Prime Minister Joseph Muscat, who is the
outgoing Commonwealth chair, said he was "elated" by Prince Charles'
"vigor" for participating in the Commonwealth. Further a Sky Data
poll conducted before the agreement found 44% of Britons backed the Prince of
Wales becoming head of the organization.