Buckley, having led his emotionally burning charge into his office, demanded he shut the door. Lumumba slammed it and continued. "Your problem is you are a fantastic coach and one of the greats of the game. You have fantastic football knowledge but you lack sensitivity and you lack emotional intelligence."

That was the 2014 confrontation that was identified as the final broken pillar in Lumumba's 199-game, 10-year career with the Magpies, a career built on strong foundations and during which he became a premiership player, an all-Australian and a long-serving member of the club's leadership group.

Having put up with the nickname "Chimp" because he wanted to fit in at Collingwood, Lumumba felt he had opened himself to his teammates and coaches about his lifelong insecurities about the colour of his skin. He had called a team meeting in which he also compared racism with homophobia. And his coach Buckley, he felt, had mocked him.

That incident provides one of several dramatic punctuation marks in an intriguing documentary to premiere on SBS On Demand on August 27. It is a film recounting Lumumba's life - or two lives really - which he describes this week as "navigating two different worlds. One playing football for the biggest club in Australia" and another recounting his travels through spiritual heartlands in North Africa and Brazil as well as his early days as a child with black skin in a predominantly white family.

Since leaving the game due to concussion last year after an occasionally acrimonious negotiation and ultimate settlement with Melbourne, Lumumba, the son of a Brazilian mother and Congolese father, has, in his words, escaped "the football bubble". He has been travelling and living overseas since March in a journey that has proved healing and educating.

It became something of a sport among the football fraternity to make light of Lumumba's passionate stand on his own identity, his private demons and his stand against racism in which he was often accused of becoming blinded by political correctness.

Probably this happened from the time he changed his name from Harry O'Brien back to his birth name and underlined by his farewell speech to the Magpies at the 2014 Copeland presentation, when he told the assembled that his given name Heritier meant prince. "The one who will have the last laugh and the one who is gifted." He finished fourth in the best and fairest that season.

Speaking from his base in Los Angeles in an exclusive interview with Fairfax Media to promote Fair Game, Lumumba said that a series of racist incidents and specifically the treatment of Adam Goodes had led to him losing faith with Collingwood and in the AFL's multicultural programs. He had become the AFL's first multicultural ambassador in 2006.

"I lost complete confidence approaching anyone in the AFL on issues of race," Lumumba said. "There was no one to go to and protocols were outdated.

"The players' association visit the clubs once a year. They don't talk about racism, they talk about racial vilification. It was always 'don't say this, you can't say that' - and the AFL itself doesn't really understand racism.

"Their total lack of education about racism leads to a total lack of education among the players. To say I didn't experience racism even at Melbourne from some supporters would be an absolute lie.

"Now the AFL is reaching out to culturally diverse and Indigenous communities because they realise it was an opportunity to expand their market. Not because they want to create harmonious communities. Not because they want to deconstruct racism."

Lumumba said when the AFL told former Gold Coast Sun Joel Wilkinson not to speak publicly about being racially vilified he became disillusioned with the multicultural program and - in 2013 - quit being an ambassador. "They [the AFL] completely silenced him from speaking about his case. That was a big opportunity lost for the league.

"Initially I was very enthusiastic about the multicultural role. I went in there full of hope until I saw the way they worked those issues internally."

He remains unwilling to discuss his relationships with Buckley and Eddie McGuire. Of Collingwood's leaders during his time at the club only Mick Malthouse and Nick Maxwell contribute to Fair Game. Maxwell says of the "Chimp" nickname that Lumumba, with whom he was close, had never communicated to him that it hurt. Collingwood on Friday said the nickname came about as a result of an incident at a party and was short-lived.

Speaking of Malthouse's care for him after the suicide of his stepfather on the eve of the 2011 season, Lumumba also says in Fair Game of Buckley's ascension, "I could see there was going to be a big culture shift at the club".

If the Buckley confrontation was the final straw, Lumumba identified his decision to take on president McGuire the previous year over the King Kong jibe as the beginning of the end. And it came, he believes, when he was enjoying the best form of his playing career.

He uses an early and oft-repeated coaching mantra to explain why he spoke so strongly on social media taking McGuire to task, a tweet that led to an intriguing session between the two men that night on AFL 360. According to Lumumba, even the others in the Fox Footy studio that night gave him the impression they felt that he, not McGuire, was the problem.

"As a younger player you are told by your coach to 'go ... just go' ... to put your head over the ball and take charge, Lumumba said. "But I felt I was hitting my head against a brick wall."

After the McGuire comments on Triple M that had reverberated across Australia, Collingwood did not respond publicly for almost four hours. Lumumba said he wanted to contact McGuire but was advised not to by the club. So, in his words, he put his head over the ball and went.

What followed was a sense of isolation, the feeling of being "the elephant in the room" that haunted him until his last day at the club. "Employees, decision-makers identified that I had gone away from the club's virtue of side by side," he tells Fair Game, sitting on a chair in a stark room attempting to make sense of his experience.

Lumumba, who will return to Melbourne this week to visit his family before the documentary's SBS launch, recalls now: "There were definitely ramifications internally. I was accused of throwing the president under the bus to boost my own profile. It continued to be communicated to me until my last game at Collingwood.

"I wouldn't say it was the sole reason I left, but it was a big reason. To my last day it was a constant butting of heads. It was something that would eat away at me. These people who had the power to influence my livelihood didn't understand me.

"I wouldn't say it's something I regret but I will say I paid the price. As I got older and more confident to speak I became the educator and that was very tiring. I was there to play football and this became an obstacle, a barrier for me that other players didn't have to face and that wasn't fair."

Lumumba can see now that his move to call a team meeting during the 2014 season in a bid to communicate his own lifelong insecurities along with identifying the pain of racism - and, in an aside, the links with homophobia - would have proved too confronting to some of his teammates but for him it was cathartic.

As his former captain Maxwell observes on Fair Game - the documentary began production five years ago after Lumumba met the award-winning New York-based filmmaker Jeff Daniels - the session with the players and coaches was probably more helpful to Lumumba than to the others in the room.

But then, according to Lumumba, Buckley mocked his stand, which included Lumumba protesting at the nickname "Les" - short for lesbian - directed by players at teammate Paul Seedsman, following some subsequent jokes over Seedsman's haircut. "I had opened up my heart about being insecure, about being different ..."

Lumumba wanted an apology and ultimately received one - he also apologised to Buckley - but the damage was done.

The documentary does not cover his time at Melbourne but he says now it rankled him that at this club, too, there was not one Indigenous staffer based at the MCG office nor any Indigenous coaches.

"I did not see one person of colour in their administration and in my career I've never once had an Indigenous coach. The AFL loves to boast about its wonderful Indigenous talent so why aren't their talents being fine-tuned for coaching?

"You tell me Leon Davis couldn't teach footballers. He taught me things about football no one else could teach. Why was that never harnessed?"

Lumumba said his return to Melbourne in the coming days will see him deal with "unfinished business". Having spoken previously of his battle with depression he has now rejected alcohol and prescription drugs as a way to alleviate stress - a well-worn path presented to him and which he has seen others take. He meditates daily, has transformed his diet, is in a relationship with an American woman he does not wish to detail and is in a far better place than during his final year of football.

He does not expect the documentary will resonate with all Australians. "I'm well aware of this so-called white fragility," Lumumba said. "We saw that when Adam [Goodes] spoke his truth. When a person of colour speaks about his or her reality, people have an issue with confronting that reality because of the system they're in.

"I'm not looking for the approval of people unwilling to give up their privilege. Of people who are always allowed to the front of the queue. That is seen as oppression for them.

"But I hope it speaks to younger people who have been less privileged. To help them understand that even someone who has been as fortunate as I have been has struggled with the stress and the arguments and the battles. I feel I have found restoration but those battles were exhausting."

Fair Game premieres on SBS On Demand on Sunday, August 27 and screens on SBS on Sunday, September 3 at 9.45pm.