Joshua is breaking through that barrier. As a cross-over celebrity now with a following beyond the boxing fraternity, he is piling up the endorsements.
Lucozade, the family drinks company with its sparkling identity which has never before considered a link with prize-fighting, are the latest product in Joshua' s corner.
They join Beats, the trendy music sound system beloved by the younger generation whose head-phones he wears, and EQ Nutrition, a more traditional fit for boxing. More corporations are in line.
Confirmation of Joshua's widening international appeal has come with an alliance with Under Armour, the US sports clothing manufacturers.
A fast-growing American interest in Joshua is being driven by Showtime, the major cable TV network there.
To expand that lucrative market, promoter Eddie Hearn is looking to fit a Las Vegas or New York fight into Joshua's busy schedule next year. That should open up the gold mine of pay-per-view television over there.
Hearn says: "AJ is the most marketable figure not just in boxing but in sport today. The interest in him is enormous, not least because everyone is finding him such a delight to work with. He's still young and there really is no limit as to how far he can go outside as well as inside the ring."
The earnings potential is enormous but Joshua is just as interested in his legacy. He is urging Hearn to examine further-flung corners of the world, saying: "I would like to fight in Africa, Dubai, the Far East. Why not Down Under?"
There are echoes here of his idol Muhammad Ali, who famously Rumbled in the Zaire Jungle with George Foreman and completed his epic trilogy with Joe Frazier in that Thrilla In Manilla.
With youth on his side and his stature as a world-class fighter growing with every performance, Joshua has the potential to dominate boxing's marquee heavyweight division for a decade.
Saturday night's impressive first defence of his IBF world title against American challenger Dominic Breazeale - in London's O2 Arena which he keeps selling out within an hour of the tickets going on line - has convinced him that he can start mixing it with his rival champions.
"Tyson Fury, Deontay Wilder, Wladimir Klitschko," he ticks off the names. "I'm ready for all of them."
The addition of Klitschko to that roll call is intriguing. With Fury under investigation for an alleged steroid discrepancy in a drugs test after postponing his re-match with the Ukrainian champion-for-a-decade he deposed, Joshua v Klitschko becomes a tantalising possibility for a Wembley Stadium super-fight.
Wilder, America's equally big-punching WBC champion, is urging Joshua to meet him in a title-unification match sooner rather than later. If that deal can be done for November then Joshua's mandatory IBF challenger, New Zealand's Joseph Parker, may have to wait until the New Year.
Whatever the order of his next fights, the world of heavyweight boxing is Joshua's oyster.
Yet through it all he remains the same unspoiled lad who won Olympic gold four years ago. Despite being world champion he has been helping Britain's boxing team prepare for this summer's Games by frequently travelling to Sheffield to train with the squad.
Come August he will fly to Rio to support them, saying: "I know them well. I enjoy being around them. And I love the Olympics atmosphere."
It seems there is no escaping a little hate on the likes of Twitter. But come on, with Anthony Joshua, what's not to like?
George Groves has hauled himself off the canvas yet again to climb within touching distance of a fourth shot at the world super-middleweight title which has eluded him thus far.
Not only revived but in some aspects reinvented by new trainer Shane McGuigan, the Hammersmith Saint dispelled many of the doubts about his chin and his stamina in out-pointing hard-man Martin Murray over 12 gruelling rounds in the fight of this Saturday night at The O2.
If the WBA can sort out the mess surrounding their championship, Groves may yet achieve his life-long ambition.
