QUEEN guitarist BRIAN MAY has pulled out of performing at todays Concert For Diana for fear of embarrassing himself.The rocker was due to perform a duet with Joss Stone at the tribute gig in memory of late British royal Diana, Princess Of Wales at London’s Wembley Stadium - but has cancelled the performance to work on his astronomy PhD thesis - and because he was unhappy with the organisers. He says, "I just could not get my head around the way they have arranged it. I didn’t want to risk embarrassing them - or myself ! It was too short notice for such major changes."I have chatted to Joss and we are going to create something new together soon." Stone adds, "I only called him up a few days ago going, ‘Why don’t you play some chords during my duet.’. I’m always trying to organise things last minute. But he needed more time to prepare, which I totally understand."