Activists wearing “Where is Peng Shuai?” T-shirts claim they were confronted by Wimbledon security staff who warned them against approaching spectators and political messaging at SW19. Nine-time champion Martina Navratilova expressed her anger at the move after the campaigners posted a video online saying they were stopped and questioned. The group of four men from the Free Tibet campaign said they came to Wimbledon to “raise a bit of awareness” about the Chinese tennis player, a former doubles world No 1. The 36-year-old disappeared from public view for weeks last…