As Novak Djokovic steps up his pursuit of history and bids for an Olympic title in Tokyo, the World No. 1 admitted on Thursday he never truly believed winning a calendar Golden Grand Slam would one day be possible. 

History beckons for the Serb after victories at the Australian Open, Roland Garros and Wimbledon, with Djokovic seeking to emulate Steffi Graf’s unrivalled achievement from 1988 when she swept all four majors and took gold in the women’s singles in Seoul.