Lawrence Okolie
Lawrence Okolie won the vacant WBA continental cruiserweight title with his victory over Isaac Chamberlain on Saturday night

Anthony Joshua hopes that rival Joseph Parker is fit and prepared for their heavyweight unification showdown in Wales next month, warning that no-one wants to be flattened in the opening rounds after such fervent and lengthy build-up to an eagerly-anticipated clash.

The two champions are due to collide at Cardiff's Principality Stadium on 31 March in a bout that will see Joshua attempt to add Parker's WBO belt to his collection after claiming the WBA (Super) and IBO straps with a stunning 11th-round stoppage of Wladimir Klitschko in April 2017.

The 2012 Olympic gold medallist, IBF title-holder since his emphatic early destruction of Charles Martin in 2016, retained his belts in October with a controversial 10th-round victory over resilient challenger Carlos Takam, who took the fight on short notice after mandatory challenger Kubrat Pulev suffered a shoulder injury while sparring.

With less than two months to go before that second consecutive date in the Welsh capital, Joshua appeared to warn New Zealand native Parker that he better be ready to go beyond the first two rounds.

"I hope he's training well," the 28-year-old told Sky Sports when asked if he had a message for his opponent. "I hope he's fit, because you know what it is right, people wait 10 or 12 weeks for us to come together and no-one wants to lay down in the first or second round.

"I hope he's fit and he's ready for a good fight, because I am."

Joshua was appearing at London's O2 Arena on Saturday night, where he had a ringside seat for protege Lawrence Okolie's points victory over fellow cruiserweight Isaac Chamberlain.

Okolie's Olympic teammate Joshua Buatsi decimated Jordan Joseph inside two rounds on the undercard, while young super-welterweight Ted Cheeseman came through a tough test against American Carson Jones.

Speaking after his eighth successive professional victory, Hackney's Okolie signalled an intention to fight on the Joshua-Parker undercard against someone like Welsh boxer Craig Kennedy.

"Isaac tested me, this is a benchmark and I want to push on from this," he said, per The Sun. "I want to have a little rest, I want to box on the Anthony Joshua undercard next. I knew it wouldn't be pretty, I hurt him early.

"I have nothing but respect for him and his mental fortitude. I'm nowhere near the finished article, there's a lot of mental and physical work to do."

Only one undercard fight has been officially confirmed for Joshua vs Parker thus far, with WBA Super mandatory challenger Alexander Povetkin set to put his WBA Inter-Continental and WBO International heavyweight titles on the line against Liverpool's David Price.