British police Armed Response Vehicle (ARV) officers take part in a Metropolitan Police training programme for armed officers when responding to a terrorist firearms attack in London on December 2, 2015. The training exercise simulated an armed police response to a Paris-style attack at a shopping centre. AFP PHOTO / POOL / YUI MOK -- EMBARGOED UNTIL 0001 GMT WEDNESDAY DECEMBER 2, 2015 -- NOT FOR USE ON ANY PLATFORM INCLUDING INTERNET UNTIL 0001 GMT WEDNESDAY DECEMBER 2, 2015 - EDS NOTE: Police shoulder number pixelated by photographer to prevent identification / AFP / POOL / YUI MOK (Photo credit should read YUI MOK/AFP/Getty Images)
