Grant Hackett has capped a remarkable comeback from addiction by earning a 2015 world titles team berth at the national swimming championships in Sydney.

Hackett, who has overcome a high-profile marriage break-up and a string of well-publicised controversies, described making the team as “one of the biggest achievements” in his life.

The dual Olympic champion clocked one minute 46.84 on Sunday night to finish fourth in the 200m freestyle final and earn a relay spot for July’s world titles in Kazan, Russia.

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Hackett and Tunisian Oussama Mellouli on the podium in Beijing. Photo: Getty

Cameron McEvoy (1:45.94) defended his national title, ahead of David McKeon and Thomas Fraser-Holmes.

Hackett needed a top-six finish in the 200m final to secure what at first seemed an unlikely relay team berth.

It is a remarkable achievement for Hackett, who has trained for just six months after a six-year break.

The result caps an amazing turnaround for the 34-year-old, who last year flew to the US to undergo treatment for a sleeping pill addiction.

But his professional demons went back as far as his last major meet, the Beijing 2008 Olympic Games, where he was denied a record third straight 1500m gold medal.

Tunisia’s Oussama Mellouli touched out Hackett in China.

“I will be honest. I hated the sport for a long time,” Hackett said.

“I got scared getting into a bathtub.

“To discover a love for something that has been such a big part of my life is really pleasing now because I don’t walk away with that taste of Olympic silver in my mouth by a few hundredths of a second.

“I can really enjoy the sport for what it is now.”

The dual Olympic champion, whose marriage to singer Candice Alley broke down in 2012, endured a string of controversies.

Police were called to a domestic disturbance at the couple’s home in October 2011, amid reports Hackett was drinking to excess.

He lost his contract as a Westpac ambassador the following year, although he continues to work for the company.

“It was a challenging few years and I had to live it pretty publicly,” Hackett said.

“One thing I am good at is listening to people around me.

Ian Thorpe’s comeback ended in 2013. Photo: Getty

“I never sit there and feel too sorry for myself for too long. I take accountability for my actions – right or wrong.

“I tried to make the best steps forward – that is all I have ever tried to do.”

Hackett said the fourth-placed finish was one of the moments he was most proud of, given how far he had come.

“In many ways it’s a different sort of achievement,” Hackett said.

“If you asked me 10 years ago (about) making a relay team and that being the only thing I was on the team for, that would be bitter disappointment, right?

“But now it’s like one of the biggest achievements of my life to make that team after such a long amount of time off – and in only such a short preparation.”

Hackett is the latest swim hero from yesteryear to try his hand at a comeback, following in the footsteps of Ian Thorpe and Michael Klim.

Thorpe’s career was ended at 30 by a shoulder injury in 2013 after he failed in his bid to make the 2012 London Olympic team.

Klim retired when he was 34 after a disappointing 14th place in a butterfly semi-final at the London Olympic trials.

– with AAP