The legendary Beatle repeatedly “got cold feet” over the project, which was filmed in his native city of Liverpool, England, the Late, Late Show host recalled.
Speaking at PaleyFest LA 2021, James said he sent a heartfelt email to Macca, pleading the case for the singer-songwriter’s participation.
The show had already scouted locations, he told Sir Paul, and cancelling at the eleventh hour would cause a big financial hit. He promised the segment would turn out “great”.
Sir Paul apparently wobbled multiple times, and even considered pulling the plug on the morning of the shoot, according to James. Fortunately, the star finally agreed to get back on board when he was told to enjoy himself.
The Carpool Karaoke segment itself saw the pair driving around Liverpool, with Sir Paul visiting someone of his old haunts and singing Penny Lane on, well, Penny Lane, obviously.
James also got misty-eyed when they performed Let It Be together.
After it aired, Sir Paul secured his first chart-topping album as a soloist in the United States and, according to James, texted him to say: “We did it. Thank you for convincing me to do it. I had a blast.”
Check out Corden’s comments here:
And see the “Carpool Karaoke” segment here:
A version of this story previously appeared on the US edition of HuffPost.