LOS ANGELES​ — The​ day​ the​ Cavaliers agreed​ to​ trade Kyrie​ Irving​ to the Boston​ Celtics,​ LeBron​ James​​ was signing jerseys for Upper Deck in Santa Monica, California.

When then-coach Tyronn Lue, also in California at the time, found out what was about to happen, he drove out to see James and put him on the phone with Cavs general manager Koby Altman.

James was adamant on the call — do not trade Irving, especially to the Celtics. By the end of the call, according to four separate accounts of people present for the conversation, Altman told James the trade would not occur.

Minutes later, on Aug. 22, 2017, word broke that the Cavs agreed in principle to send Irving to Boston for Isaiah Thomas, Jae Crowder, Ante Zizic and Brooklyn’s 2018 first-round pick.

James’ close friend, Randy Mims, and bodyguard Rob Brown came to him with their phones to show him the news. James, who was still signing jerseys, dropped the pen and slumped in his chair.

“Everyone knows that when Kyrie got traded it was the beginning of the end for everything. It’s not a secret,” James said in an interview with The Athletic.

James suggested he didn’t feel he was lied to by Altman, so much as Altman was overruled by owner Dan Gilbert.

“You realize at that point in time, take nothing from Koby, because Koby (was just named GM), but at that point in time, you realize that Koby’s not the only one running the team, as (former GM David Griffin) had done, and that’s why Griff was let go pretty much,” James said.

Cavs front-office officials declined to be quoted for this story but disputed that Altman gave James any indication the trade would not occur. They also said Altman asked James whether he would commit to the Cavs long-term if Irving were not traded, and James said no.

On Wednesday, James will walk into Quicken Loans Arena as a member of the Los Angeles Lakers for his first game against the Cavs since leaving the organization a second time as a free agent.

“I’m returning to a place where I’ve spent 11 years of my career,” James said. “I had some great moments, had some not so great moments, but, all in all, when you give everything to whatever, the franchise, a teammate, a coaching staff, anything, that’s all that matters.”

It wasn’t supposed to be this way. When James made his triumphant return to Cleveland in 2014, after four years and two titles in Miami, he said more than once that he intended to retire there.

Then, the next four years happened: an astonishing mix of amazing, heartbreaking and truly bizarre. Not even LeBron expected he’d so quickly be able to bring Cleveland its first major pro sports title in more than 50 years, and certainly not in such dramatic fashion. Nor could he predict that the title, along with his philanthropic work in his hometown of Akron, would cement his legacy in Northeast Ohio regardless of where he finished his career. He had no idea Kevin Durant would stack the deck in Golden State, or that his own team would lose the general manager he trusted, then trade away the other elite player he depended on — at Irving’s demand, no less. Or that one of his closest teammates would unspool one of the greatest performances in NBA Finals history by forgetting the score of the game.

There has been some assumption that one of the biggest factors in LeBron leaving Cleveland was his strained relationship with Gilbert, a strain that is both well-documented and overblown. It wasn’t like they were close before James announced on TV in 2010 he was headed for South Beach, and Gilbert responded with the Comic Sans letter, nor had they become friends when James chose to return to Cleveland.

The distrust between them was always there. When they struck a new partnership in 2014, James stuck to his job of playing at a level to put the Cavs in the Finals, and Gilbert kept his word to spend the money necessary to keep the team competitive.

Initially, the organization bristled at James’ method of doing contracts — signing one-year deals instead of a long-term, maximum contract like the three guaranteed years he gave the Lakers in July. When James felt the roster needed upgrades in season, or if he felt a change was needed at head coach, he let it be known through his body language, his commentary and his play.

But after the Cavs won their first and only title in 2016 — the city’s first since 1964 — James did something that summer for which he receives little credit. He signed a multiyear contract, for two seasons with a player’s option for a third.

Yet that same summer, the balance of power in Cleveland’s boiling rivalry with the Warriors shifted for good as Durant, a former MVP, shocked the NBA by signing with Golden State. And after Durant and the Warriors beat James and the Cavs in five games in the 2017 Finals, James, for the first time, headed into the summer without either freedom of movement or leverage over the organization.

So when Griffin, the general manager who’d built the Cavs’ 2016 championship team and whom James trusted, didn’t get a new contract from Gilbert when his old deal expired, there was nothing James could do about it. When Irving was traded, there was nothing he could do about it.

There is nuance with the Irving deal. When Irving demanded to be traded in July 2017, he did so in large part because he no longer wanted to play with James.

Irving, in fact, told the Cavs he wanted out so badly he’d go ahead with knee surgery and miss a large portion of the year if he wasn’t traded. James, who did little to try to bridge the divide with Irving, told the Cavs to keep Irving in spite of his threats.

Then there is Griffin, who before he parted ways with the organization knew Irving was unhappy and had already explored some ideas of his own to trade Irving — just not to the Celtics, and not for a deal in which the most valuable asset the Cavs were getting back was a draft pick for future use. Griffin’s idea was to leverage Irving’s desire for change as a way to acquire Paul George, another elite player who would have helped James try to win now. But he wasn’t going to do it without first getting a new deal from Gilbert, or without talking to Irving and agent Jeff Wechsler to make sure of Irving’s feelings.

None of that ever happened. Griffin and Gilbert never came to terms on a contract. Enter Altman, 34 at the time, promoted from his position as Griffin’s second assistant. By late July, Irving’s trade demand had become public, and the Cavs, believing the situation between Irving and James could not be fixed, began fielding offers, feeling Irving’s value was at its highest.

But as James noted, Irving was under contract for two more seasons in Cleveland, which made this trade demand different from the situations San Antonio and Minnesota would go through with players like Kawhi Leonard and Jimmy Butler. Moreover, James, Lue and other players and coaches felt the uncertainty around Isaiah Thomas’ injured hip should have been a deal breaker. Once it wasn’t, from that moment forward, James felt Gilbert was taking a more active role in basketball decisions and was in effect trying to pivot away from an organizational structure centered on James.

Nearly everything after that was a struggle — the team’s new acquisitions never jelled and were eventually traded for other players who also sometimes wrestled to fit in. James played in every game, regular season and postseason. The playoffs brought two seven-game series, and James won two postseason games on buzzer-beaters. And when the Cavaliers improbably reached the Finals again, and James scored a playoff-career-high 51 points in Game 1, the Warriors took it to overtime on the heels of a few costly Cavs miscues, including JR Smith’s forgetting the score with the ball in his hands inside of five seconds left. Golden State won the series in a resounding sweep.

Once it was all over, James, once more a free agent, took a family trip to the Caribbean to consider his options. Believing the Warriors could not be toppled by what he had in Cleveland, especially with Irving gone and not replaced by anyone near his caliber, he chose where it would be most comfortable for his family to live and prosper while he finishes an illustrious career that is currently in year 16. He’ll be 34 in December.

Last week, James passed former Lakers great Wilt Chamberlain for fifth on the all-time scoring list, wearing a Lakers jersey, on a day when the temperature in Los Angeles reached 78 degrees.

James’ agent, Rich Paul, watched the game at Staples Center sitting next to Terence Nance, who will direct “Space Jam 2,” starring James. Arnold Schwarzenegger was there, as were Adam Sandler and Cindy Crawford and Nipsey Hussle and Flea and Floyd Mayweather Jr. Just a typical Wednesday in L.A.

James’ primary business interest, SpringHill Entertainment, is more successful than ever and headquartered in Hollywood. His eldest son, LeBron Jr., a budding pro prospect as an eighth-grader, can play against optimal competition out west.

“I felt this was my next step,” James said. “I don’t like to dwell on the past too much. People get sensitive when I talk, I don’t like ruffling people’s feathers and things of that nature. It was just meant for me, meant for my family going forward.”

James scored 44 the night he passed Chamberlain. Last night, he dropped 51 points against another of his former teams, the Miami Heat, in their building.

The Cavs, meanwhile, are in a total rebuild. They are 2-12, owners of the worst record in the NBA, and are heavily scouting college players and pros in Europe for the upcoming draft. Veterans left behind by James were rankled early this season when it was apparent the organization would not try to contend for the playoffs, even after being told by Altman it would.

James said as he returns to Cleveland this week, he’s looking forward to stopping by his I Promise Akron elementary school, and maybe visiting his suburban mansion with his mother (his wife and sons will spend Thanksgiving in Los Angeles). He also said he’s not expecting a reaction from Cavs fans anything like what he was met by in 2010, when he came back to Cleveland for the first time as a member of the Miami Heat.

“Shit, it better not be,” he said, referring to the flaming pile of hate and vitriol few had seen inside a pro sports arena.

Regardless, he’s prepared for whatever comes.

“It doesn’t matter if it’s negative, because the only thing that matters is what I gave to the city, what I gave to that community, what I’m still giving to that community,” James said. “It doesn’t matter. At the end of the day, they have one obligation and that’s to cheer for their team. And I’m not on the team.

“And personally I’m in a whole different space than I was in 2010, so shit doesn’t bother me.”