If you had walked along the NSW-ACT border a few years ago, you would have likely spotted a rickety old railway bridge on the industrial outskirts of Canberra. Transport for NSW demolished the unused bridge in 2018, apparently because too many vehicles had hit it and bits of track were starting to fall onto the road. Its destruction was lamentable, because it played a remarkable role in our history.

When Soviet diplomat and undercover spy Vladimir Petrov was arranging to defect to Australia in 1954, he would drive out to that bridge and stuff papers between its wooden planks, for ASIO men to find and collect. Petrov’s defection – and the dramatic one of his wife Evdokia at Darwin airport two weeks later – captivated Australia and the world. It epitomised the drama and fear of the Cold War.

Soviet couriers escort Evdokia Petrov across the tarmac at Darwin Airport in 1954.

Espionage ain’t what it used to be – for starters, you don’t need old railway bridges to hide your communications when you can encrypt them in a WhatsApp message instead – but ASIO boss Mike Burgess made it clear last week there are still people working in Australia to harm our national progress and to further the interests of other sovereign powers. And the threat they pose is higher than it ever was during the days of the Petrovs and the Cold War.

In his annual threat assessment, Burgess said foreign interference was of as much concern to ASIO as terrorism. He went into unprecedented detail about several incidents and gave four reasons why Australia is a target: our strategic position and alliances; our leadership in science and technology; our economic activity; and our defence upgrades.