When Michael III started to favour another courtier, Basiliskianos, Basil decided that his position was being undermined. Michael threatened to invest Basiliskianos with the Imperial title and this induced Basil to pre-empt events by organizing the assassination of Michael on the night of 24 September 867. Michael and Basiliskianos were insensibly drunk following a banquet at the palace of Anthimos when Basil, with a small group of companions (including his father Bardas, brother Marinos, and cousin Ayleon), gained entry. The locks to the chamber doors had been tampered with and the chamberlain had not posted guards; both victims were then put to the sword. On Michael III's death, Basil, as an already acclaimed co-emperor, automatically became the ruling basileus.