Royal Tour: Prince Harry and Meghan open ANZAC ceremony, prepare for Invictus Games

Opening the renovated ANZAC memorial at Sydney's Hyde Park, Harry was not just a Prince, but a veteran who knows the cost of war.

Dressed in formal military attire, Prince Harry and wife Meghan, in a dress designed by Kiwi Emilia Wickstead, laid a floral wreath to remember the dead and officially open a Centenary Extension to mark 100 years since the First World War.

Inside lies dirt samples from 100 fields where Australian soldiers died in battle, including two pieces from the Waikato in tribute to the New Zealand wars.

It was also a tribute to those who died not just for country, but for Britain and the Royals themselves.

"It's always poignant that the royal family take these opportunities to commemorate the service of people from New Zealand and Australia who travelled so far to battlefields, so far from home, in the name of the King," said Billie Moore, the New Zealand Consul General in Sydney.

The Duke and Duchess of Sussex will continue to pay tribute to servicemen and women on Saturday night with the Invictus Games opening, where Prince Harry is expected to give a speech.

For Ben Peckham, post-traumatic stress surfaced when those around him noticed strange behaviour, like preferring to sleep on the street and being agitated.

"I hit rock bottom some years after leaving the service," he said.

Taking part in the Invictus Games in discus is part of Mr Peckham's journey back to health, but the number of returned defence personal with PTSD is unclear as not every puts their hand up.

But Gareth Pratt said that is changing as Princes William and Harry bring it to the fore.

"They both must have friends and comrades and other servicemen that they have seen gone through it, so their ability to use it for a tool and to promote others - yeah thank you. I just thank them," he said.

Mr Pratt was working on the frontline as an army medic when he realised he was displaying the same signs he was telling others to get counselling for.

He is co-captaining the Kiwi Invictus team and it is just as much about building mental strength as physical.

"The one thing I learnt is the routine, the sport, the exercising regularly, talking to other people, even doing this interview, enables you to get a little bit of help. It is just that one little word that I might say in that interview that could help someone else out there," he said.