Theresa May's "enough is enough" response to yet another deadly attack on British soil will not just shape the final days of the election campaign but marks an important change in the way Britain's mainstream political leaders talk about the scourge of Islamist-inspired terrorism.

Appearing outside Downing Street hours after three men used a rented van and knives to kill seven people and injure dozens more near London Bridge on Saturday night, the Prime Minister could have employed a measured tone in her first public statement given there are just four days to go until Britons cast their votes and political campaigning had been suspended.