Back on this day in 1967...
Studio Three, EMI Studios, London
From 4:30-5:00 pm, in Room 53, without the Beatles in attendence, "All You Need Is Love" was mixed into mono. Between 7:00 and 11:30 pm, the job was done again, this time with the Beatles on hand. An acetate pressing of this latter mix was given to Derek Burrell-Davis, director of the BBC outside broadcast team for June 25th.
Note: A studio two session booked for the evening of June 22nd did not take place.
Source: The Complete Beatles Chronicles - Mark Lewisohn