Having been firmer and sterner than all other leaders in his initial response to the MH17 catastrophe, Tony Abbott is now cautioning against ''facile optimism'' in the difficult days ahead.

The man whose blunt language articulated the world's initial shock, anger and outrage and set the tone for subsequent responses, now appears to be opting for a more measured and nuanced approach.

He was right then and he is right now. Armed with more information than those who spoke before him, Abbott called the disaster for what it was - a crime - and pointed to Russia's culpability, direct or indirect.

Now, the challenge is to ensure that the resolution moved by Julie Bishop and carried unanimously by the Security Council is implemented in full and that the Russian leader is true to the commitments he has given.

That will require patience, diplomacy and ingenuity.

Our Prime Minister, it should be noted, was less constrained than many of his counterparts in the immediate aftermath, and remains so. In what John Kerry calls a ''complicated world'', the Americans, for instance, need Russian co-operation to advance their objectives in dealing with Syria and Iran.

Similarly, Malaysian Prime Minister Najib Razak had to negotiate with the leader of the rebels for custody of the two black-box data recorders and the guarantee of safe access to the crash site.

Less constricted, Abbott could reflect on the bigger picture while giving voice to the families of victims. In opposition, he projected no passion for global affairs and even opposed Labor's pursuit of a seat on the Security Council.

In government, he has formed productive relationships with counterparts, shown a firm grasp of policy and, through Bishop - the minister who has been the standout performer of his government - made maximum use of that Security Council seat.

In tragedy, he has also shown the capacity to reach out and, in the words he used to describe Bishop's address to the Security Council, ''call it for the world''.

Released from the self-imposed shackles of his narrow, slogan-driven domestic agenda, he has also appeared more prime ministerial. The surprise, especially for those unfamiliar with his empathetic side, is that it has come naturally.

Abbott defines the task ahead as retrieving the bodies, securing the site, conducting the investigation and securing justice, and it has two related dimensions: giving comfort to the grief-stricken and ensuring that the resolve of all the key players does not weaken.

The big question so far as the four tasks goes is ''how'': how will the remaining bodies be retrieved; how will the site be secured; how will the investigation proceed; and, most crucially, how will justice be done?

The message from the Prime Minister's latest briefing is that we simply don't yet know many of the answers. The solemn promise is that the guiding principle will be to do the right thing by the families of those who died until all questions are satisfactorily answered.

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