To put us back on topic...
Yeah, I remember there was a concert in Liverpool for John's 50th birthday... I was there!!! It was held at Albert Dock and was absolutely huge! Unfortunately Paul, George or Ringo didn't attend - but Paul and Ringo did send personal messages via a large screen with Paul playing his PS Love Me Do mudley (yes, MUDLEY!) and Ringo singing I Call Your Name (backed by Tom Petty and Jeff Lynne etc).
Yoko and Sean appeared though - they came on stage at the end to tremendous cheers. Yoko was going to make a speach but she broke down in tears as the whole crowd began chanting Give Peace A Chance - it was extremely moving. In the end she had to leave the stage accompanied by Sean.
There was a video of it released a good few years back, I don't know if it's on DVD though - here are the details taken from my copy of the video: