But all too familiar across the APS is the kind of professional dilemma Mr Yannopoulos saw in his late 30s, realising he wasn't going to make it to retirement age staying solely in the area he had specialised.

User-centered design, design thinking, and thinking about people's experiences. These ideas are on the lips of ministers and APS heads now, and highly sought-after skills across the public sector. But at the turn of the century Mr Yannopoulos could well have been seen as a bit of a radical among all the technical tax experts at the ATO talking about user experience. Simplifying the business activity statement design from one that Mr Yannopoulos says was probably technically perfect to one that was usable was not how things used to be done. The ATO was probably ahead of its time, he admits - so he stayed until he became its chief design officer.

"I'm a bit nerdy in the sense that I actually love this stuff," he says, as if that explains why he took the harder path of ever-increasing challenges in portfolios from Defence to Health to Education - where the childcare subsidy implementation that would earn him a Public Service Medal was plagued by tensions between the different portfolios and all the red flags.

"Why people talk about it is probably that it's the first time we quite clearly created a single senior responsible officer in the public sector and it was very clear to me from both of the ministers at that time 'if this doesn't work out it's your fault'," Mr Yannopoulos says.

They needed to get 14,000 childcare providers into a new system, and about 18 software providers had to redevelop their products to interface with the Commonwealth payment system.

Mr Yannopoulos was the only new person on the program that year that it all turned around, so it wasn't about additional capability. They knew how to do it, he says, like making peace with the software developers because they hadn't been engaged well and bringing childcare providers on side. Families too, about a million of them, needed to be convinced to use myGov because the scale was too large for registering by phone. Mr Yannopoulos remembers going to the minister to get on the front foot convincing families to use the digital government platform, telling him: "It has a reputation, which it earned that is no longer really true ... be assured I will get the thing working."

It took everything he'd learned in his career to that point, he says. Stakeholder engagement, getting ministerial authority, and something he learned from the ATO: keeping open a platform every week for anyone on the program to raise issues so they could be solved and quick decisions could be made.

This month Mr Yannopoulos steps from one of the broadest jobs in government - Finance's deputy secretary for budget - into one of its biggest jobs - associate secretary for Defence. That's not a role for radicals but for people who have an exceptional track record of implementation and an even more exceptional understanding of change.

As if the eye-watering sums of money involved in programs under his new leadership aren't enough, the mantle is also seen as a natural stepping stone to the secretaries board. At 49 he's still young enough to be a competitor to the policy types also vying for the top jobs for many years to come.

Martin Parkinson, then department secretary of Prime Minister and Cabinet, sounded the alarm several years back that implementation skills "should never be seen as the poor cousin of policy development".

Mr Yannopoulos has his own perspective on why implementation skills are critical, noting trust in government is influenced by people's interactions with it, not just how the media portrays it. If the experience of applying for the childcare subsidy was terrible, it wouldn't matter who was in government or whether it was the private sector or public sector administering the processes, they'll think poorly of the government.

"It's going to take time because there's still a lot of senior people who grew up in the policy identity. It ain't just about policy work now - you've got to do more."

Mr Yannopoulos identifies three areas, based on his own experiences in the public sector, where the APS could sharpen its thinking around future leaders.

Project management has to be grown across the public sector, he says. Delivering well is how government builds trust, and this government has shown its interest in being much more directly involved in delivering services to Australians on the ground, such as in disaster and resilience.

APS professions should be expanded to include project management and finance to teach the best expertise as agencies are where the Commonwealth spends.

Finally, Mr Yannopoulos wants to see change in how the APS engages with stakeholders and does policy development. It has to get much better at talking to the Australian community, less through representative groups and more on the ground. "How do you know a program is working? There's all this folklore about the Canberra bubble - this place ain't like anywhere else in Australia, so you're out there having a look. That's just a challenge for the public sector."

It's a great time to work in the APS, he says. There are diverse cultures across its organisations - a feature not a bug - but it still struggles to reconcile that with a desire to do things in a consistent way while acknowledging that different organisations are pursuing different goals.

"We probably do want the culture at Health to be different than the culture at Defence. They are pursuing different goals. I would be OK if the accounts payable was done the same way in both places, lean and efficient. But of course it's not."

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