Meet the new Malcolm Turnbull. Steely jawed. Resolute. Alert and alarmed as he tells Australians they face "a growing threat from Islamist terrorism".

Note the words. "Islamist terrorism". Violent, murderous jihad aimed at maximum carnage, maximum terror, in the name of religion. 

Just days after the vicious London attack from which two Australian nationals are still unaccounted, Turnbull is dealing with another - apparently a deranged copycat - at home.

The cumulative effect has suddenly become insurmountable, necessitating a marked shift in official rhetoric, and potentially, a further hardening of laws as well.

Gone was the reassuring balm of an Australian exceptionalism - the "most successful and harmonious multicultural nation in the world".

Gone too, the front-footed defence of Islam as a religion of peace, as much a victim of extremist violence as the godless west.

Assuming these views are still held, they have been left unsaid this time amid the king tide of violence - that script relegated to the lesser-known too-soft basket.

In its place, the lethal threat within, and crucially, a series of "very grave questions" from the Prime Minister over the resolve of state-run criminal justice systems to contain potential agents of death.

"I have raised these today with the Victorian (Labor) Premier ... how was this man on parole? He had a long record of violence. A very long record of violence. He had been charged with a terrorist offence some years ago and had been acquitted. He was known to have connections, at least in the past, with violent extremism. But he was a known, violent offender ... how was he on parole?" the PM intoned.

Clearly, there are political motivations here, and a spot of good old fashioned blame-shifting to boot.

But Turnbull can no more alter the facts than he can wish the security situation onto a higher moral plane.

Clearly, there are political motivations here, and a spot of good old fashioned blame-shifting to boot

His assessment is threefold. First, this terrorist threat is clear and present and will substantially define his government for as long as it lasts. Even before the Melbourne incident, he had warned that the situation would get worse before it got better. Second, public opinion is shifting as fear rises. Thus reassurances about unity and trust are losing their punch, and worse, now risk sounding like an apologia. Third, as a result of the above, Turnbull faces a ready-made opposition within as the new security hawks, Tony Abbott, the ex-SAS commander Andrew Hastie, and others, scan his responses for any sign of weakness.

These political realities dictate that Turnbull will hence-forth err on the side of toughness.