The Suez crisis and the choice of Eden's successor led in 1957 to the first major personal criticism of the Queen. In a magazine, which he owned and edited, Lord Altrincham accused her of being "out of touch". Altrincham was denounced by public figures and slapped by a member of the public appalled by his comments. Six years later, in 1963, Macmillan resigned and advised the Queen to appoint the Earl of Home as prime minister, advice that she followed. The Queen again came under criticism for appointing the prime minister on the advice of a small number of ministers or a single minister. In 1965, the Conservatives adopted a formal mechanism for electing a leader, thus relieving her of involvement.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): When was a formal mechanism for electing the Minister adopted?
1965