Speaking at the security council chaired by Donald Trump, she addressed Russia’s foreign minister Sergey Lavrov, who sat two seats down from her, furiously scribbling notes as she spoke.
Saying that Britain had been attacked by two Russian agents named by aliases Alexander Petrov and Ruslan Boshirov Mrs May said Britain had clearly laid out its position by charging the pair with attempted murder.
She earlier said it was regrettable that Russia continues to prevent the Security Council from holding the Assad regime to account, while the Syrian delegation looked on, arms crossed, and unimpressed.
During her speech to the gathered world leaders, she told Mr Trump: In meeting Kim Jong-un you have created a historic opportunity.
Lavrov had to wait for the Netherlands, Kuwait and China to have their say before he was allowed the opportunity to respond.
And he did so by accusing Mrs May of promoting unsubstantiated, ideologically-inspired rhetoric that had no factual basis.
If they do not want to cooperate, does this mean they have something to hide he asked.