Mike Pezzullo rose through the ranks of the public service to occupy one of the most powerful positions in Canberra as head of Home Affairs in the Department of Defence. In 2009, he wrote a major policy document warning of the threat posed by a more aggressive China – before Xi Jinping came to power.

Last year he fell from grace when more than 1,000 personal text messages between him and Liberal Party powerbroker Scott Briggs were revealed by Nine newspapers. Their political content led to an investigation by the public service commissioner and his sacking.

Five months on, and Pezzullo is making his first cautious steps back into public life, giving a speech last week to a conference about civil defence in the age of war. He spoke to 7.30's Sarah Ferguson.

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