Geldof, who arrived with Sinead O'Connor and was joined by two of his daughters, Fifi and Pixie, gave the stars a pre-recording pep talk, sounding, he said, "like the headmaster".
But it was an emotional moment, singer Emeli Sande said afterwards. "Bob gave a really touching speech, so that really got everybody in the mind frame that we needed to be in to remind us that it's fun but we're here for a really serious reason."
Geldof had been keeping quiet about who would sing the opening line - in 1984 it was Paul Young. There had been wide speculation that it would be Chris Martin of Coldplay, especially after the no-show of Adele. In the end it was One Direction.
The lyrics to the Band Aid 30 version of the song have been changed too, to reflect the different cause. Several of the lines from the 1984 song were heavily criticised for being clumsy and patronising, including the one about no rivers flowing in Africa - the continent of the Nile, Congo and Niger.
One Direction and Emeli Sande took part in the Band Aid 30 remake. Photo / AP
"And tonight thank God it's them instead of you" - that unmistakable Bono-voiced line - has also gone. This time he sang: "Well, tonight we're reaching out and touching you."
There was a change in the attitude of the British Government, too. Yesterday the chancellor, George Osborne, announced via social media that he had spoken to "the remarkable" Bob Geldof: "Told him we'll waive VAT on #BandAid30 so every penny goes to fight Ebola." In 1984 Prime Minister Margaret Thatcher refused to allow sales tax to be waived on the original Band Aid single before finally relenting under Geldof-led pressure.
The single is released today.
- Observer