london britons join islamic state militant group syria iraq hunt kill britain new defence minister say gavin williamson say britons go syria iraq fight islamic state hat britain stand air strike could use estimate 270 british citizens still quite simply view dead terrorist cause harm britain williamson tell daily mail interview publish late wednesday everything destroy eliminate threat say add believe british fighters join islamic state never allow return unite kingdom williamson 41 defence minister little month replace michael fallon quit sexual harassment scandal prominent british militants mohammed emwazi know jihadi john sally jones reportedly kill british u.s. force since travel fight islamic state death jones know white widow fallon say british nationals choose leave uk fight islamic state legitimate target britons join islamic state hunt kill defence minister