Foreign Minister Julie Bishop was attending a 68-member coalition counter terrorism meeting in Washington when her British counterpart and former London mayor Boris Johnson was told of the deadly lone wolf attack on Westminster Bridge.
Ms Bishop has told Sky News she was about to make her contribution to the meeting, hosted by US Secretary of State Rex Tillerson, when the British foreign minister was led out of the room.
"I didn't notice it at the time but when the moderator went to call on Boris Johnson next and he wasn't at his seat, some thought 'typical Boris, he's wandered off somewhere'," she told Sky News on Sunday.
But Mr Johnson had at that moment been given the news of the attack, in which a man mowed down pedestrians on the bridge and fatally stabbed a policeman before being shot dead by authorities, as other attendees began glancing at the smartphones realising something had happened in London.
Ms Bishop said Mr Johnson returned to the table and addressed all coalition members about the unfolding events.
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"He was visibly shaken, he is a former mayor of London, he knows and loves that city," Ms Bishop said.
Mr Johnson was still very deeply concerned when she spoke to him later.
"It was the idea that an individual can take a vehicle and use it as a weapon to kill innocent people, to kill civilians that is so deeply troubling," he said.
She said terrorist gangs can be tracked and kept under surveillance, but if someone is self-radicalised and acts alone, and as in this case uses a motor vehicle to mow people down in a public place, it is "nigh-on impossible" for intelligence and security agencies to detect that in advance.
