The UK should be worried about a high-level online attack because there is a lack of talented and skilled cyber experts, according to a senior figure from the intelligence agency GCHQ. The top spook is concerned the organisation might not have the right people to deal with a sophisticated assault on the UK's online networks.

In an effort to find new talent, the Cabinet War Rooms in central London have been hosting the Cyber Security Challenge - a 24-hour simulated cyber-attack. The scenario is based on an assault by a foreign government on the UK's financial systems. As part of the 24-hour exercise, teams of young cyber defenders have been shown fake news reports, given briefings by the national defence community and tip-offs by undercover operatives.

Stephanie Daman, chief executive of Cyber Security Challenge UK told Sky News that people in the competition have the right sorts of skills, but none of them are currently in the cyber-security profession.

"This is what we call the hidden talent that we have in this country that we can't seem to reach out to bring into the profession."