"Enough is enough" PM May says after London attackers kill seven

By Guy Faulconbridge and Estelle ShirbonLONDON (Reuters) - Prime Minister Theresa May said Britain must be tougher instamping out Islamist extremism after attackers killed at least seven people by ramming a van into pedestrians on London Bridge and stabbing revelers in nearby bars.After the third militant attack in Britain in less than three months, May said Thursday's national election would go ahead."It is time to say enough is enough," the Conservative leader said outside her Downing Street o