The 37-year-old Maitland man, nicknamed "Burty Burt", started the run from Queens Wharf Brewery in Newcastle and finished at Macquarie Place Park in Sydney.

Burt broke the record for the fastest known time on the Great North Walk - an epic and hilly 265-kilometre trail. He finished the run in 39 hours and nine minutes, beating the previous record by 40 minutes.

He did it with a team of pacers and support crew, known as The Immortality Project. Among them was Grant Brisbin, the previous record holder, who ran with Burt for 75 kilometres.

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Burt likes to use trail running to raise awareness of mental health.

When he runs, time is of the essence in more ways than one.

"A lot goes back to our primitive beings and what we evolved to be before we became westernised," he said.

"There's not enough time for people to switch off and not worry about their lives."

Runners, though, can get to a point of thoughtless trance in which time alters.

"There are times where I've done an 8-, 10- or 12-hour run and it feels like you've been out there for an hour. You get to a state where you're not worried about anything. You're just in the motions and not thinking about time. Time just flows."

Burt did the Newcastle to Sydney run - which he finished on Thursday - to raise awareness and money for mental health through the Black Dog Institute. So far, he's raised about $10,500.

He believes people are far more capable of moving forward than they realise.

"As hard as that is, things will eventually start to get better. Things might not get easier, but you do become stronger.

"One's strength isn't determined by the ability not to break, but the ability to keep going once broken."

He said connection between people is an important part of good mental health.

"It can be just checking in on mates. Even the smallest connection can have the biggest of impacts, which I think can sometimes be taken for granted. Sometimes people don't talk about their mental health. That's all right, you can still be there for people if they don't want to talk."

Running in nature helps Burt get into the moment. Or the now, as the mystics say.

"Being in amongst the bush gives me a sense of calm, which definitely helped me a lot," he said.

Running can also be a battle between mind and body - similar to mental health challenges - with injury, suffering and pain at the heart of it.

"It's a real juggle between the mental and physical sometimes. At 63km in, I was doubting whether I could do it," he said.

He was in the runners' grip of "back and forth between your physical and mental state".

"At 63km I was moving very well, but mentally I thought I couldn't do it. Towards the end, I was done physically, my heart rate was pinging but my mind was like 'no you've got this'."

Burt was planning to run to Sydney and back, but he came down with a respiratory infection. At 50 kilometres from Sydney, his doctor advised that the longer he kept going the worse the infection would get.

"I had to make a call. The plan was to try to do the fastest known time to Sydney, then turn around and do the overall fastest known time as well.

"When the decision was made that we wouldn't be turning around, it was a hell of an effort to push on with the infection.

"My throat ended up that inflamed, I couldn't take in food anymore. It can end up becoming quite dangerous. I ended up losing 9 kilos over that 39 hours."

His heart rate spiked to 204 beats a minute towards the tail-end of the run. He battled through rolled ankles and a snapped pole used for grip, as well as sickness. His doctor got him a script for the infection.

"I actually started taking antibiotics on the run. That definitely helped," he said.

Fatigue was a big barrier, with sleep deprivation leading to micro-sleeps that heightened the risk of falling.

Despite the challenges of running, Burt advocates for it.

"Even if it's only a few kilometres to get the endorphins going. The fitter you feel, the happier you become with the freedom of movement. It's definitely good for the mind and soul."

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