Legendary pop star Robbie Williams reunited with his former Take That bandmate Mark Owen for the first time in 12 years on stage. Robbie, 49, was in the middle of performing at the Sandringham House in Norfolk when he brought out special guest Mark, 49, in front of the 20,000 fans.The pair performed Take That tune Greatest Day together in the grounds of the royal residence which had been turned into an eco-friendly concert for the night on Saturday.