It was an expected, but nevertheless welcome outcome for Britain on a day which was further brightened by silver medals for Anthony Whiteman in the 1500 metres and Francis Agyepong in the triple jump.
After pulling away from his nearest challenger around the final bend, Ladejo found that he had time to signal his victory. And being Ladejo, he did, slowing 10 metres from the line and sticking one finger up into the air before crossing the line in 46.12sec.
As a gesture, it had far more to recommend it than the ones he had made at Glasgow last month, which skirted uncomfortably close to mockery of his opponents.
Ladejo was punctiliously respectful to the three other finalists yesterday, but in truth they were never serious rivals, with Pierre-Marie Hilaire finishing a long way back to take silver in 46.82. Nor were they encouraged to be as Ladejo put his race together with complete efficiency, taking the lead as the lanes broke and then drawing steadily away.
Where this leaves him in relation to world, or even British 400 metres running is not yet clear as the Olympics loom ever closer. But it had not escaped Ladejo's attention that his time had beaten the Globe arena track record belonging to the world champion, Michael Johnson, who recorded 46.29sec five years ago.
"It's the first step to the man," he said with a grin, although he was happy to acknowledge that it could be a long walk.
After missing virtually the whole of last season because of a belatedly diagnosed problem in his back, Ladejo always intended to use these championships as a means of getting back into racing fitness.
"These rounds have done exactly what I wanted them to do," he said. "It felt easy out there today. That is what it is meant to feel like. I can run a low 46 and it feels like a stroll in the park." He is now confident that he can beat David Grindley's three-year-old British outdoor record of 44.47sec, and can be running 44.3 early in the season.
"I've beaten all the Americans out there that I have to beat except for Michael Johnson. It's a matter of progression. And I've taken another big step here," Ladejo continued.
It completed a good championships for Ladejo's coach, Tony Hadley, who also looks after Britain's 60 metres silver medallist from Saturday, Jason John.
Agyepong has previously been best known for facts unconnected with his athletic career. He works as a sous chef at Christopher's, on the Strand in London, and was used as the model for Lenny Henry's character in the television comedy series, Chef.
Now, however, at the age of 30, he has made a personal breakthrough in this event by claiming his first international championship medal.
It looked for a while as if that medal might be golden. Having headed the previous day's qualifying with a personal best of 16.97, Agyepong took the lead in the first round with 16.93.
It lasted until the third round, when Maris Bruziks, of Latvia, equalled the distance and went ahead on the basis of a better second-best jump. Agyepong could not raise his game, and the Latvian consolidated his position with a final jump of 16.97.
Agyepong's initial reaction was one of disappointment, because he had hoped to beat Keith Connor's British indoor record of 17.31m. "I felt so good in qualifying that if I had had another jump I think I would have broken it. But I've got to be happy with silver."
Like every other triple jumper in the world, Agyepong is operating under the shadow of Britain's world champion, Jonathan Edwards.
"What Jonathan did last year made me change my outlook," Agyepong said. "You can't let this guy get so far ahead or it's not worth competing against him. A lot of guys were crushed and messed up by what he did last year. But now you have to start thinking about jumping 18 metres to be able to compete with him. I think three others can go over 18 metres this year."
Whiteman ran a hugely positive race in the 1500m, taking responsibility of a slow race 800 metres out and holding off all-comers until the final 10 metres, when Spain's world indoor silver medallist, Mateo Canellas, forced his way past. At 24, and almost 6ft 3in, Whiteman now stands out as a major force in British middle-distance running.
Grit Breuer, of Germany, returning to international competition after a three-year suspension for a positive drug test, won the 400 metres in a time - 50.81 - that will send a shiver along the spines of her potential Olympic rivals.
Britain's total of one gold and three silver medals put them ninth in the overall table behind the leaders, Russia. But the final day belonged to Spain, who had four track victories. Thankfully, they have a bearable anthem.
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