David Beckham has urged Manchester United's flops to prove they are motivated to play for the troubled club. Former United star Beckham was in Manchester on Thursday to attend the premiere of a new documentary about the club's 1999 treble-winning side. Beckham was a key figure in the United team that won the Premier League, Champions League and FA Cup under legendary boss Alex Ferguson. Now the former England captain's Studio 99 company have played a role in the production of '99', a three-part series that launches on May 17.