Billy Bragg posted a photo of himself and Dick Gaughan and wrote: "Thanks to Celtic Connections for inviting me to be part of the John Maclean centenary concert last night in Glasgow. Many highlights, but singing The Red Flag with my old pal Dick Gaughan was a special moment. Having been unable to perform for many years due to poor health, he was on great form and received a standing ovation when he took the stage."