On Diamond, Lulu said: "[He] has such an incredible body of work that this show will be amazing. I'm absolutely thrilled to be a part of it."
MacDonald reportedly received a personal invitation from Diamond. She said: "To be able to perform on the same stage as Neil Diamond is an amazing honour for me. I listened to his music growing up and his hits are legendary. It will probably feel like a dream and quite nerve-wracking to be on the same stage."
Elton John will be performing first tonight, featuring guest performances from Plan B, Leon Russell and Rumer. Robert Plant will perform on October 29 with Band of Joy and the London Oriana Choir.
Diamond's performance will be on October 30, and will be aired live on BBC Radio 2.