Wladimir Klitschko, wearing blue jeans and a black shirt, stepped into the ring beside Joshua as Eddie Hearn, Joshua's promoter, announced that the two men would fight each other at Wembley Stadium on April 29.
What an occasion that will be. If Tyson Fury's ascent to the world title at the end of last year always felt like a false dawn, Joshua looks like the real deal, a man with the charisma and class to breathe new life into what has been a moribund division for so long.
It will be the toughest test of Joshua's career by a distance and there are still some who fret that he is not ready to face a man with 40-year-old Klitschko's ring-craft.
But Joshua is not a fight baby any more. He is 27 and this was his 18th straight win.
Add to that the fact that Klitschko looked desperately unimpressive in his defeat to Fury and it is an intriguing match-up. It will certainly be a 90,000 sell-out and Hearn said it would be 'the biggest fight in British boxing history'. He is probably right.
Joshua stung Molina with a sharp left hook towards the end of a first round that he dominated completely. The second followed a similar pattern. This time, it was a left upper cut that rocked Molina backwards. Again, Joshua was untroubled.
Molina offered very little offensively and Joshua tried to find his range with his destructive straight right. He found it, sure enough, in the third.
It connected with Molina's chin and left him crumpled in the corner. Joshua stood there for that moment, then retreated as Molina, somewhat improbably, clambered to his feet and beat the count.
The referee waved the fight on and Joshua swarmed all over Molina. It was over in seconds. Joshua connected with a big left and when Molina began to crumple again, the referee stepped in. The fight had lasted two minutes and two seconds into the third round.
Joshua told his audience: 'We move on to a bigger arena, more people can view it. This is the step up people have wanted. Klitschko wants his belts back, may the best man win. I focus on myself, that's how I beat Wladimir Klitschko.'
It had been a spectacular end to a thrilling night of heavyweight boxing. Joshua's victory had been preceded by an epic battle between Dillian Whyte and Dereck Chisora.
It had started out as a pantomime with a build-up that threatened to make a laughing stock out of both men but they fought a contest full of courage and indomitability and won the respect not just of the sell-out crowd but of each other.
Through almost every one of the 12 rounds of their WBC world heavyweight title eliminator, the fight between the two bitter rivals swung one way and then the other.
The result was desperately tight but Whyte, the reigning British heavyweight title holder, won by virtue of a split decision. The verdict was met by some boos from a crowd who thought that Chisora had edged it but they knew they had seen a terrific bout.
The build-up had grown increasingly fractious and last Wednesday it boiled over again at the final press conference when Chisora picked up a table and threw it at Whyte.
The fracas prompted the British Boxing Board of Control to rule that Whyte's British heavyweight title would no longer be on the line. But it was still classed as a final eliminator for the chance to face WBC champion Wilder and as fights go, it was quite a support act.
