Jay-Z left London commuters star-struck over the weekend when he and good friend Chris Martin took the Tube to the rapper's O2 Arena show. The '99 Problems' rapper played a sold-out concert on Saturday evening (12th October) at London's O2 Arena, and made his way there by taking the London Underground from Waterloo to Greenwich.Capital Fm Jay-Z was joined on his commute by supporting act Timbaland and surprise duet partner Chris Martin from Coldplay, who joined Jay-Z on stage to perform 'Heart Of The City (Ain't No Love)' during the show.