I got my first reference at 6.40 am - still in bed and a bit groggy but I definitely heard Chris Evans tell a listener, No - the mystery guest was not going to be Paul McCartney.

And he popped up again - exactly 12 hours later - in a Times2 article (p4) about Burt Bacharach.  Apparently his "walls are peppered with framed keepsakes - a thank-you note from Paul McCartney,..."