I just finished reading Andy Williams' 2009 autobiography Moon River and Me
where he mentions the first televised Grammy Awards which he hosted and on which John Lennon appeared as a presenter with Paul Simon:
"John Lennon didn't typically do television but he agreed to this appearance; it may have been because it took his fancy or because he was returning a favor I'd done for him a couple of years earlier."
Williams had supported John during his deportation issues. He went on to talk about how much fun he had with John at the party afterwards. He received this hand-delivered letter the next day:
March 9 or 10? 1975
I enjoyed meeting you at Discogrammy, we both did. Hope you got home OK. A couple of as got to talking about you the next day and we ended up thinking what a great job you would do on my song Bless You. so i thought, what the hell, i'll tell you! i've never written a letter like this before, i'm worried in case i come off like some kind of 'promo' man. anyway i've done it now, all the best to you.
p.s the typings mine all mine!
He didn't take John up on the offer but he did frame the letter and still had it on his office wall when he wrote this book.