Anthony Joshua is sparring with Charles Martin

Anthony Joshua has revealed that he has been sparring with Swedish southpaw Otto Wallin ahead of his world title fight with IBF champion Charles Martin.

The 26-year-old is preparing to challenge American champion Martin for the IBF heavyweight title at the O2 Arena on April 9, live on Sky Sports Box Office.

Martin will be the first southpaw that Joshua has faced as a professional and the former Olympic champion has been sharpening his skills in sparring sessions with Wallin, another heavyweight who leads with the right hand.

Joshua posted a picture of Wallin on his Twitter account, saying: “Great work today with my southpaw sparring partner.”

Martin has since responded to news of Joshua’s sparring sessions by tweeting: “We will see if that’s enough though.”

Joshua previously shared the ring with Wallin while they were both amateurs, beating him on points at the Haringey International tournament in 2010.

But the Swede is yet to suffer a defeat in the paid ranks, with 10 of his 14 wins coming inside the distance.

Wallin has not made a ring appearance this year, but he fought five times in 2015, picking up three stoppages and two points wins.

Joshua will attempt to become a heavyweight world champion in only his 16th fight, joining current No 1 Tyson Fury, who holds the WBO and WBA ‘super’ titles, and WBC champion Deontay Wilder.