Charles, Prince of Wales studied at Trinity (1967–70) during Butler's time as Master. Initially it was thought that he might study an "ad hoc" course; a humorous cartoon showed Butler telling the Prince that he was to study a specially made-up history course "in which I become Prime Minister". Instead Butler recommended that, unlike previous members of the Royal Family, Prince Charles live in College, study for a normal degree and sit Finals like any other undergraduate. After initial reluctance, the Palace agreed. Butler was publicly promoted as a mentor and counsellor to the Prince, making himself available for a 45-minute time slot each evening before dinner should the Prince wish to seek his advice. He turned a blind eye to Prince Charles keeping a car in college (in breach of the rules) but exclaimed "Hell no!" when the Prince asked if he might join the Labour Club. He also gave Lucia Santa Cruz, his research assistant for his memoirs, a key to the Master's Lodge and often let her stay, which gave rise to rumours that he was facilitating a romance between her and the Prince. Butler's appointment to the Order of the Garter on 23 April 1971 was seen as a gesture of recognition for his guidance of the young Prince.