Novak Djokovic and Andy Murray have known each other for a quarter of a century. They played from the age of 12, meeting 36 times as professionals, including 10 Grand Slam matches.

It will be all business when Andy Murray coaches Novak Djokovic at the Australian Open. While the partnership between two of the biggest rivals in recent men’s tennis history has awakened feelings of shock,

Jannik Sinner will launch his Australian Open title defence under a stubborn doping cloud but the whiff of scandal may do little to halt the Italian juggernaut. Sinner remains the man to beat at Melbourne Park even as doping officials seek a two-year ban for the world number one for failing two drugs tests last March.