The Foreign Secretary has told ITV News: "We must never give in and will never give into terror.
"British foreign policy can never be dictated by terror. Murder can never be excused by any political grievance.
"This has shocked the country and the whole world."
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It comes after shadow chancellor John McDonnell made a surprise U-turn on the Tory budget vote which is due later today.
Georgia Williams could have been saved if police had not missed several chances to catch her killer, a review found.
Jennifer Connell complained the injury made it difficult for her to "hold a plate of hors d'ouerves" at a party recently.