Novak Djokovic’s bid for an unprecedented 21st singles Grand Slam title at the Australian Open could hinge on a single answer he gave on a visa form—had he travelled between Serbia and Spain in the fortnight before his arrival? 

The 34-year-old is reported to have ticked the box saying ‘no’, but social media posts and reports appear to show the Monte Carlo resident was in the Serbian capital Belgrade and then Marbella in the 14 days leading up to his departure for Melbourne.