His beauty, his grace, his style, his presence and — until what stunned admirers must now understand to have been the very end — his youthful, boyish openness. These made up Chadwick Boseman’s persona; an actor who had come to be loved among many things for his lightly worn imperiousness, humour and charm as T’Challa, king of the fictional African country Wakanda in the Marvel smash Black Panther. Like many actors who play kings and princes in hugely successful movies or TV shows, the regality rubs off, the royalty is a residue, but he had these things anyway.

What makes his death so shocking for me is that I had so loved his performance in Spike Lee’s new film Da 5 Bloods, playing the squad leader Norman, who was killed in action in Vietnam, 50 years before four of the men under his command (played by Delroy Lindo, Clarke Peters, Isiah Whitlock Jr and Norm Lewis) now come back to present-day Vietnam on a fraught journey into their own pasts. Lee brilliantly recreates flashback jungle scenes for all five, but with the four middleaged as they are now, and Chadwick Boseman’s Norman as he was then, as he was in their memory. He has grown not old as those that are left have grown old: he is still the impossibly handsome and daring young leader who has the tragic military burden of persuading his men not to mutiny because of the racism of the top brass.

This superbly conceived performance now assumes an almost unbearable, real poignancy: when I see the poster image of these men taking a knee at Norman’s graveside it is overwhemingly sad. We now know that Boseman was being treated for cancer, and must already have been aware of the possibility that his end was near.

It had been Boseman’s destiny, also, to dramatise other African-American icons on his way to becoming an icon himself: in 42, he was legendary Jackie Robinson, the first black American to make it into baseball’s major league.

This was a film which notably chose a simpler, inspirational theme over anything more complex and politically contentious, but Boseman’s performance was what supplied the complexity and texture in itself: seductive and determined, intent on surpassing his own loneliness and the prejudice of others. His Robinson was a figure shown being beset by bigotry on all sides, even by some on his own team, but toughing it out without self-pity. Already, he was assuming a kind of superheroism.

In Marshall, he played Thurgood Marshall, the first African-American Supreme Court Justice of the United States, appointed to the bench by Lyndon B Johnson, who made important rulings against segregation. The movie dramatises an early courtroom drama, when his Marshall had to defend a black man accused of raping a white woman, and Boseman let rip with gorgeous and extravagant theatrics as the brilliant young advocate.

Something of the same physicality and athleticism — and also sexuality — went into his portrayal of James Brown in the flawed biopic Get On Up, which, though it could not quite get to grips with the more unwelcome side of its leading character, had another exquisitely fierce turn from Boseman.

In 21 Bridges, he had a more conventional, generic role as a New York cop who in time-honoured style had lost his dad to criminals, and now has to solve a violent gangland crime on Manhattan which he does by ordering all twenty-one bridges connecting the island to the mainland to be closed to cut off the culprit’s means of escape — an interestingly regal move.

But of course it was as T’Challa, the gloriously charismatic superhero of colour in Marvel’s afrofuturist adventure, that Boseman imposed his personality on the movies. He was sensitive, handsome and stylish with something introspective, vulnerable and self-questioning in his manner as he assumes the surreal throne. Boseman did it all with such grace that it is an incidental pain for his fans that he never got to reapply these acting gifts on playing Shakespeare on stage or screen.

Like all celebrities and movie stars, Boseman was entitled to his privacy, even though through his sheer empathy and lovability, his fans had come to think that they were already part of that privacy, that they knew him. So the news that he also had cancer is such a shock. He seemed — he was — so young, always appearing at least a decade younger than his years. His great movie roles were quintessentially about youth, about the vigour and energy and idealism and having it all in front of you. Boseman now becomes the lost prince of American cinema, who had a glorious and inspirational career.

• This article was amended on 30 August 2020 because it was Lyndon B Johnson, not John F Kennedy as an earlier version said, who appointed Thurgood Marshall to the US Supreme Court. Kennedy appointed Marshall to the US Court of Appeals.