The Brooklyn Academy of Music recently staged a rare production of the entire Henriad—“Richard II,” “Henry IV” Parts I and II, and “Henry V”—by the Royal Shakespeare Company. The Henriad is rarely performed in sequence (the last time it was performed in the United States was in 2004, by the Trinity Repertory Theatre, in Rhode Island), because, for one thing, it’s exhausting for actors. The sheer number of lines is daunting, and the actor playing Prince Hal must turn himself from a rakish layabout enthralled by his lowlife friend Falstaff into Henry V, who has inherited the heavy crown his father has wrenched from the head of Richard II (played in this production by David Tennant). That last part of the role has been thoroughly inhabited in recent years by the 1989 film version directed by and starring Kenneth Branagh. (In England, there seems to be a tie for the best “Henry V” between Branagh and Alan Howard, who played the title role in a 1976 production, directed by Trevor Hands, at the R.S.C.)

In this recent production, Alex Hassell played Prince Hal, the prodigal son who grows up to be a roguish king. Hassell, whose sultry good looks bring to mind Sal Mineo in “Rebel Without A Cause,” is now back in London, where he is preparing to direct “Macbeth” at the collaborative theatre company, the Factory (whose credo—in contrast to the R.S.C.—is “no sets, no advance sales, no press, secrecy, no promises of casting or expectation of commitment, and lasting as long as our audiences and/or we are interested”). In preparing to play Hal, Hassell told me, “For me, the question going in—and I was massively terrified—was, why does Hal do what he does? Is it all as it seems to be? Part of the job is to scrape away the ether around what people think of as the Henry of the St. Crispin’s speech and ‘Once more unto the breach.’ ”

“You mean like ‘Boyhood’?” a friend said, when I was trying to explain my Henriad weekend. Richard Linklater’s 2014 movie, which records a boy’s childhood and adolescence, took twelve years to film, and runs for a hundred and sixty-five minutes: the Henriad is nine hours, not counting breaks for snacks and riding back and forth to Brooklyn on the A train. The experience that may come closest to watching the Henriad is viewing condensed, consecutive segments of the British documentary “7 Up” series, directed by Michael Apted, in which the same British children (now adults) are interviewed every seven years; the most recent one, “56 Up,” was released in 2013.

The Henriad—billed at BAM as “King and Country”—is about war and what power means and the ways that people contrive to get it, but it’s also a journey play, and part of the myth of the journey play is that the hero must overcome obstacles. Hassell continued, “In the journey plays, the hero is given a weapon by his mentor, who I think is Falstaff”—brilliantly portrayed by Antony Sher in this production—“and the weapon that Falstaff gives to Prince Hal is role-play, subterfuge, and the element of surprise.” I mention that onstage, playing the wastrel Hal in “Henry IV” Part I, Hassell seemed nervous. (His father, Henry IV, is played in this production by Jasper Britton.) He laughed. “I was nervous! Henry is nervous! I’m playing a boy, and then a king who is bullshitting. Henry is in over his head! I was in over my head! Henry is exceptionally complicated and difficult. He’s confused, morally and tactically, about what he is doing. He’s trying to learn very, very quickly how to behave. He is pretending to be a warrior king. He trips and picks himself up. By ‘Henry V,’ which is the play we see most often, he says, ‘I will go now and conquer the French,’ and then he goes and conquers the French. If you play it that way, there’s no play! You must portray his doubts, his self-loathing, his emasculation in the face of his father, all of which is at odds with what people see Henry V as being.”

Hassell paused. “And he stays conflicted. By the time he gets to France, he’s thinking, I’m a man who has brought all these people to their deaths because I’m a fuckhead. But then, when the losses to the British side are so small, he feels that God has blessed him from above. It’s an extraordinary moment. In the scene with Katharine, he’s saying, ‘I’ve killed as a king but can we rule with love?’ He hopes that the relationship can be redemptive, that he can become a different king because of it.”

Audiences through the centuries have been thrown by Prince Hal’s banishment of Falstaff in the last act of “Henry IV,” when Prince Hal assumes the crown after his father’s death, and becomes Henry V. The Shakespearean scholar Stephen Greenblatt maintains that the character of Falstaff is based on Richard Greene, a contemporary who dismissed Shakespeare as “an upstart crow,” and was famous for his huge appetite. If so, Falstaff, on whom audiences dote, gets his comeuppance. When I asked Hassell about the repudiation, he shot back, in Prince Hal fettle, “He has no choice. On his deathbed his father has said to him, ‘My friends must be your friends.’ That eliminates Falstaff. But also, really, Falstaff has acted so completely without faith. He sold people to their deaths! He mutilated Hotspur’s corpse! Early on in rehearsal Greg”—Doran, the Royal Shakespeare Company’s artistic director—“said that for Hal, Falstaff is like a drug. He needs to put that ten-mile radius between them so he will not be tempted.”

Watching a person grow up, we know what we hope will happen to him—luck in love, fortitude, a vocation—and what we hope will not, but we know we can’t know for certain. We can only cross our fingers. (I, at least, wouldn’t want to know—it’s an unbearable thought.) Plays are different. There have been years I have been unable to watch “Hamlet.” I now find myself veering from “Lear.” At a remarkable production of “The Seagull,” a number of years ago, at The Royal Court in London, I thought, before Konstantin kills himself, Oh, it can’t happen, it must not happen, someone stop him. A few winters ago at the movies, watching the film of “Far from the Madding Crowd,” in which the heroine chooses the wrong man, and then compounds her mistake, one of my daughters leaned over and whispered, “Oh no, so many bad decisions in such a short time.” I felt like this, watching Hassell’s Prince Hal. You want to catch him as he falls. And then shake him.

Gregory Doran has been the artistic director of the R.S.C. since 2012; last year he directed Hassell as Biff in Arthur Miller’s “Death of a Salesman.” When I asked Doran about Prince Hal’s evolution, he said, “There is a very strange speech right at the beginning of ‘Henry IV,’ when he alludes to a plan. He says, basically, that he will shine brighter later for having been sullied. Often directors simply cut it, which seems to me reductive. Hal is more reflective then he seems, but the keynote must be an air of improvisation. Alex plays Hal in the moment. This is a young man whose behavior is crazy and erratic, but is saying, ‘I do have a plan, I’m just not going to tell you what it is! I know what my responsibilities are.’ ” He paused. “I also find this story resonates now in the press, in England just now, as Prince Harry’s behavior is under such scrutiny. There’s an interesting parallel between this Prince Harry and Shakespeare’s Prince Hal. Of course, the current Prince is not the Prince of Wales, but remember, neither was our Harry. Until his father took the crown from Richard, he was just a rich aristocrat.”