The FBI told a federal court it needed a search warrant to look at thousands of Hillary Clinton’s emails on the laptop of former US congressman Anthony Weiner because they had potential to cause “grave damage to national security” if disclosed. The wording was contained in a redacted search warrant and other court papers that were previously under seal until Tuesday in the investigation of an online relationship between Mr Weiner, the estranged husband of top Clinton aide Huma Abedin, and a teenage girl in North Carolina.