Sue Barker introduces live coverage from day two of the 2015 Wimbledon Championships at the All England Club. Petra Kvitova begins the defence of the ladies' singles title she won convincingly against Eugenie Bouchard in 2014. Her main rival will be Serena Williams, who is aiming to claim a sixth singles title. Only two women have been more successful than her in the Open era - Martina Navratilova, with nine wins, and Steffi Graf, with seven. Show less