US Secretary of State <a gi-track='captionPersonalityLinkClicked' href=/galleries/search?phrase=John+Kerry&family=editorial&specificpeople=154885 ng-click='$event.stopPropagation()'>John Kerry</a> (R) holds a joint press conference with British Foreign Secretary Philip Hammond (not pictured) after their meeting at the Foreign and Commonwealth Office (FCO) on June 27, 2016 in London, England. US Secretary of State <a gi-track='captionPersonalityLinkClicked' href=/galleries/search?phrase=John+Kerry&family=editorial&specificpeople=154885 ng-click='$event.stopPropagation()'>John Kerry</a> urged EU members not to lose their heads over the referendum.