The clip, which has attracted more than 2 million views to date, was produced by Adut's alma mater, Western Sydney University. Adut, who was conscripted at six years old, had never been to school. He came to Australia as a refugee aged 14, taught himself to read, write and speak English, and won a scholarship to study law in 2005.

Adut had also applied to Macquarie University but, in July 2005, Drew Fraser, a Canadian-born law professor at Macquarie, made headlines when he wrote that Australian was courting disaster by admitting Sudanese refugees, who would bring with them crime, violence and social problems. He later added that sub-Saharan Africans had an average IQ of 70-75. Apparently, they were not only incorrigibly criminal, but bordering on stupid. 

Fraser was suspended by the university, and subsequently took early retirement, but his comments were enough to sour Adut on Macquarie.

"It did hurt me a lot," he says. "People forget that if you have such attitudes, such negative ideas, it will actually affect the way people think, the way they react, and eventually people will give up and assume that person is quite right. But I know that is wrong. I speak my dialect, I write my dialect, and I speak a bit of Suri, Shilluk, Nuer. He can only speak English. If I gave him a good test in some of my dialects, he would get zero. What does he know about my language? I speak Arabic. Does he? Can he write Arabic?"

Adut and I meet in Le Pub, a subterranean bar and bistro in the CBD. It's my choice for lunch, as Adut does not normally eat during the day. Despite its generic name, Le Pub serves a very creditable menu of Parisian bar food, stripped of the scarier offally stuff. Unlike Adut, I eat all day long. Although it's only 1pm, this will be my second lunch, so I opt for the chicken salad, since salad is not really a meal. Adut chooses pan-seared john dory fillet with duck-fat potatoes and pippies. He seems to enjoy it but, it is probably fair to say, Adut does not spend too much of his life worrying if his spuds are done in duck fat. He is a partner in the AC Law Group, a firm which he co-founded, and works seven days a week. He takes on fee-paying criminal trials and family law, and refugee pro bono cases.

Adut was born in 1984 in the village of Malek in South Sudan. He was one of eight children, four of whom are now dead, two from "natural diseases", he says, "and two from war", as if war were an unnatural disease. Adut was taken from his mother, ordered to walk to Ethiopia, and forced into the army at the age of six. Discipline was murderous. Children were executed by firing squad, and their friends were made to watch them die. The army provided them with almost no rations, and Adut contracted "all kinds of diseases that a child can get". He spent time in a primitive hospital in Ethiopia. He had two nephews and two cousins in the army, and one cousin slept beside him in the ward. 

"We slept on the ground," says Adut. "The bedsheets were corn sacks. We were little, so we could actually get in them and pull them up like a blanket. He died next to me." Dozens of others died in the hospital. "The hospital would be cleared every day. Cleared of dead people. Dead kids.

"I went a little bit mad," says Adut. "I went crazy somehow. I'd cry daily." 

He recovered, but later stepped on a nail and suffered an infected wound in his foot.  "It was excruciating," he says. "The aftermath of that became almost the worst experience I could get. There's a small insect, almost like a flea, called a jigger. It used to go back to the wound, seal it, and then it would blow up. It nearly made me crippled. It kept eating in my skin. You take it out, you clean it up, you thought it was gone, and another one would come. It was almost consistently getting worse." Then came cholera, dysentery and malnutrition. "I was remanded in bed for months and months. I was a skeleton. I couldn't get up. One of my relatives told me 'I want you to die', because I was poking him with my bones, my skeleton. I attempted to commit suicide but I couldn't roll out of bed. I was too weak."

He says he was in hospital three times, and I get the feeling the details may have blurred for him into one mass of misery, plagued by fever and the proximity of the death.

In 1994, after further military training in Ethiopia and South Sudan, he went to war. "I got shot in my back," he says, "and had a shrapnel wound in my hip." He was recuperating in a heavy-artillery area when he met a soldier whose sister was married to Adut's brother, John. Like the rest of his family, John had thought Adut was dead. When he heard he was alive, John decided to take him out of the army and smuggle him to Kenya. Adut escaped by night, hidden under sacks of corn. He and John spent 18 months in a camp in Kenya before their visa for Australia was approved in June 1998. They arrived in Sydney with John's wife and son. Adut had just turned 14.  

"The first day was terrible," he says. "If I'd had a ticket, if I'd had money and a way to go, I was going to leave the country. It was just too cold. Everything. It was a completely different world, different ways, different people, different faces. Nearly everyone was white." Adut's skin is almost the colour of ebony. Indians, Asians, even Aboriginal people, all looked white to him. He did not know how anything worked. "I remember blowing up a microwave," he says, "because I put in a cold Coca-Cola tin to warm it up."

Adut had no education. "I tried to get to high school," he says, "but I was 14, the people that were there, they were kids. Where do I start? Year 1? Year 2? Year 3? Kids used to laugh at me for the couple of days I was there." 

He studied instead at TAFE. He learned to read and write using dictionaries – "Maybe I've got about 40 dictionaries," he says – and with the help of friends he made it through playing soccer, taking part in athletics, and studying the Bible. It was, he says, a "hard, hard, hard thing to do".

He worked in Coles, and at a service station, a meat factory, a workshop that made doors and windows, and a fish shop. But all the time he continued his studies. He enrolled in an accountancy diploma, did well in taxation law and business law, and applied to Western Sydney University for a place on the Bachelor of Law program. The university had him sit a couple of first-year courses to see if he could succeed, then offered him a scholarship as a full-time student. Again, Adut found it difficult, but he had help.

"It takes a lot of courage for someone to do a law degree," he says. "It also takes teamwork from your lecturers and your friends." He graduated in 2010, and completed a post-graduate diploma and starting   practising in 2011. The next year, he went back to South Sudan and found his mother. "It was the best feeling I've ever had," he said, "just to have a mother again, to be a kid again. My mother sat me in her lap and she's so old and so wrinkly. Her body is like a map that you can trace for yourself the suffering she went through."

Adut's brother John completed a social-science degree, went to Geneva to take a graduate diploma in humanitarian work, then returned to Sydney to study for a Master of Law. He went back to South Sudan several times and, when fighting broke out again in 2013, he was killed. 

There has been so much hardship and pain in his life, but today Adut looks dapper and prosperous. He carries a Ted Baker bag, and wears a Wayne Cooper shirt and a Kangol cap. He leaves his plate clean and compliments the chef, but says, "I don't care if food doesn't taste good. I still enjoy it."

His growing public profile has lent his story another twist but, even before his Australia Day address, Adut was a celebrity in Blacktown. The Western Sydney University video, which showed a dramatic reconstruction of his early life, was particularly appreciated in the multicultural streets of Greater Western Sydney. "Almost everyone goes, 'That's the guy! That's the guy from the TV,'" says Adut. His fame came entirely unexpectedly.  "Those who made the video, their intention was not to make me popular or to promote me, but to help other people think about their life."

He believes it has worked. "A lot of people thank me," he says. "Most say, 'You changed my life. The stupid little things I used to think about, I've now changed my attitude to.' They've stopped drinking alcohol, or taking drugs, or they're actually going back to school or going to university and doing a degree." 

Adut has shown others what is possible. And, although he speaks with great sadness about the deaths in his family and his lost childhood in the army, Adut's anger is most evident when he talks about Drew Fraser, the academic who implied success for a Sudanese might be impossible.

"One day I'll be able to get my PhD," says Adut, "and tell him that I'm a doctor, just to prove to him that I'm now a doctor because of what he told me. I will do that, just to make sure that we're square. I'm quite happy to take a test with him, in English, Arabic, Nuer and Dinka, and see whether he'll be able to match me."