He is self coached, he relies on YouTube videos to hone his technique -- and in running-mad Kenya, he had to plead with officials to win selection for the track and field team as a javelin thrower.

Julius Yego may not have won a medal at the 2012 London Olympics but his achievement in just qualifying and then reaching the final in this specialist discipline was a triumph over adversity.

"I do not have a coach, my motivation comes from within. Training without a coach is not an easy thing," he told CNN's Human to Hero series.

But this obvious handicap did not prevent him hurling the 800-gram spear 81.81 meters -- his personal best, breaking his own national record -- in qualifying in London to join his sport's elite.

Yego eventually finished 12th in the final behind Keshorn Walcott of Trinidad and Tobago, who shocked the likes of two-time defending champion Andreas Thorkildsen of Norway to win a surprise gold.

Walcott's upset victory, only the second by a non-European in Olympic javelin competition, should act as encouragement to Yego, who is not short of self belief.

"I want to be a legend and leave a legacy," he said.

"My focus now is on the 2013 World Championships in Moscow. I am trying to be in the top three. I have to move into the medal bracket, not just in the finals."

Yego had to battle "a lot of challenges" to gain acceptance in his own country as a world-class athlete.

The 23-year-old hails from a village in the Rift Valley, the traditional breeding ground for the seemingly endless stream of Kenyan distance runners who have enjoyed such success in distances from 800 meters to the marathon.

The fourth child in a family of nine, he took up the javelin at secondary school when he realized he wasn't going to be a successful footballer.

"My first-born sister used to encourage me, my mum also, but my dad sometimes was angry with me," Yego said.

"Most of my time I was going out of school, no learning, so he was a bit angry with me. But after I proved him wrong he let me continue with this sport."

Yego briefly dabbled with the track, but at a stocky 85 kg his physique is more suited to an event like the javelin and its incredible technical demands.

It helped that an elder brother was also a javelin thrower at their elementary school, and he was also inspired by watching the 2004 Athens Games on the television.

"It just took me, I wanted to be like Andreas Thorkildsen," he said.

Little could he have realized that eight years later, Yego would be competing against his hero in an Olympic final.

With no specialist javelin coaches in Kenya, the then teenager turned to technology to see what Thorkildsen and other great champions such as Czech Jan Zelezny were doing.

"I watched YouTube and it really paid off for me, to see the training techniques and skills they are using," he said.

Yego first made his mark with third place at the 2010 African championships in Kenya's capital of Nairobi, but disappointment followed at the Commonwealth Games in New Delhi later that year as he was well below his best in finishing seventh.

His big breakthrough came in 2011 at the All-Africa Games, but he nearly did not make it to the championships in Mozambique, which were to prove pivotal to his career and eventual qualification for the 2012 Olympics.

Yego was initially told he would be going with the Kenyan team to the event, but three days later came the shattering news that he would not be making the trip.

"I rang one of the officials in our federation and I asked what was happening," he recalls.

"He told me we don't have enough cash to accommodate all of you, so I told him you can remove one of the runners so you can give me a chance!"

Yego's confrontation with officialdom clearly struck a chord, and three days later he was reinstated on the team.