Joshua, 34, went on to secure a TKO win against the Swede, before building on that success with a knockout of Francis Ngannou in March.

Reflecting on his darkness retreat, Joshua said on The Jonathan Ross Show this week: “It was completely pitch black, no sound, no communication with anyone. All your senses get shut down.

“I didn’t realise how tired I was. Just sat from Monday to Friday. It was phenomenal, a good experience and much needed.

“Would I do it again? Because I’ve experienced it once… It’s harder than I thought, but I’m stronger than I thought, so I put myself in that situation.”

The former two-time world heavyweight champion also discussed his next fight, saying: “Around September is when I’ve been told, I was hoping for June. I’ve got some time to go on dates now and mingle a little bit. I’m training at the minute, I’ve got two months before I get into training camp.

“No, [I don’t know the opponent], but I think what they’re saying is, ‘Be patient,’ because you’ve got Tyson Fury vs Oleksandr Usyk for all the belts. And then once that’s done, hopefully I can kick down the door and get my opportunity.

“[Fury] is one of my rivals. This is someone I want to compete with one day, so everything he says… I’ve got it all stored in the back of my memory, and when the fight happens, I’m going to use it as a lot of fuel.”

Fury vs Usyk is scheduled for 18 May in Saudi Arabia, with the winner set to be crowned the first undisputed heavyweight champion in 24 years.