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LONDON, ENGLAND - MAY 04:  Labour's London Mayoral candidate Sadiq Khan and member of Parliament for Tooting walks through East Street Market in Walworth on May 4, 2016 in London, England.  Londoners will go to the polls tomorrow to vote for Mayor Of London with Labour's candidate expected to beat Conservative Party rival Zac Goldsmith to the position.  (Photo by Rob Stothard/Getty Images)
LONDON, ENGLAND - MAY 04:  Labour's London Mayoral candidate Sadiq Khan and member of Parliament for Tooting walks through East Street Market in Walworth on May 4, 2016 in London, England.  Londoners will go to the polls tomorrow to vote for Mayor Of London with Labour's candidate expected to beat Conservative Party rival Zac Goldsmith to the position.  (Photo by Rob Stothard/Getty Images)

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Sadiq Khan: London still one of world's safest cities

London Mayor Sadiq Khan tells CNN's Michael Holmes people must remain "vigilant and never complacent" in the wake of a knife attack in London.

Sadiq Khan: London still one of world's safest cities

London Mayor Sadiq Khan tells CNN's Michael Holmes people must remain "vigilant and never complacent" in the wake of a knife attack in London.