Heads of MI6, MI5 and GCHQ to appear before MPs
7 November 2013 Last updated at 07:22 GMT
The three men in charge of Britain's intelligence agencies are set to be questioned by politicians in public for the first time.
The heads of MI6, MI5 and GCHQ are due to give evidence to parliament's Intelligence and Security Committee.
They are expected to be asked about terrorist threats, cyber security and leaks by the US whistle-blower Edward Snowden.
Gordon Corera reports.