Mr Shanahan's son Nathan lost his battle in 2016 after working tirelessly to help fellow veterans and emergency service crews, and John's been fighting to change the system ever since.

The Royal Commission, expected to begin in July, will examine all aspects of ADF service and the experience of those who transition to civilian life, according to AAP.

READ MORE: 'We still need to do more and more work': Walking Off the War Within returns so no one walks alone

It will look at the availability and quality of health and support services as well as issues facing ADF members and veterans including family breakdowns, housing and employment.

Mr Shanahan said he looked forward to telling Nath's story.

"I would certainly love to have input into how it affected our lives, and just how frustrating it was to try and get support for Nath," he said.

READ MORE: A veteran on average dies by suicide every 2 weeks: what a royal commission needs to look at

"Considering Senator Jacqui Lambie raised this in parliament in 2014 that there was a need for a Royal Commission into returned veterans, when you look at that timeframe, it's taken a long time.

"In that time, there have been a lot of lives lost."

While the inquiry will not have the power to change legislation, Mr Shanahan said he would be keenly watching to see every eventual recommendation fully implemented.

"Hopefully, with the chance to interview people who have been very much at the forefront of this, who have suffered losing loved ones, they'll hear very raw details of how badly the system - DVA, the whole system - has let down people who took their own lives and caused unbelievable heartbreak for loved ones," he said.

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"We'll get a very honest assessment from the people who'll be interviewed over it, it's something that can't be whitewashed, these people will be talking very much from the bottom of their heart.

"We're doing it because we've suffered the raw brunt of losing a loved one, and we want to make sure this doesn't continually happen to other people who will find themselves in a similar situation.

"We dilly-dally too much time, and we don't have time on our side, every day that goes by we're losing lives."

Mr Shanahan's annual event to raise awareness of mental health in the armed forces and emergency services, Walking Off the War Within, will take place on Saturday.

If you or someone you know is in need of crisis support, phone Lifeline 13 11 14.

Help is also available, but not limited, via the following organisations. The key message is you are not alone.

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