London Mayor Sadiq Khan said on Thursday that people "must not cower" and "allow terrorists to succeed" in destroying their way of life, a day after four people were killed in an attack outside the Houses of Parliament. “We are the greatest city in the world. This is not the first time terrorists have tried to destroy our way of life, it's not the first time they have killed Londoners. But I tell you what, we have shown in the past we are resilient, we have shown we are not going to allow them to cower, so we are going to show them that again today,” Khan said.