The London 2012 Olympic Games was at serious risk of a cyber attack, with organisers fearing that the opening ceremony could have been targeted.
Officials have revealed for the first time in an interview with BBC Radio 4 that real threats emerged ahead of the Games, as the whole country's infrastructure was put in jeopardy.
Olympic cyber security head Oliver Hoare explained that he received a call in the early hours of the morning on the day of the opening ceremony.
He described the call as outlining a "credible attack on the electricity infrastructure supporting the Games".
The main fear was the lights going out, meaning close to a billion people across the world would have seen the events unfold as they watched the opening ceremony.
However, Olympic bosses had made provisions for such an attack and included it as part of their vulnerability management strategy.
"We'd tested no less than five times the possibility of an attack, a cyber attack, on the electricity infrastructure," confirmed Mr Hoare.
If a loss of electricity had occurred, he confirmed to the BBC that a backup plan was in place that would switch the system to manual, with various technicians in place ready to step into action.
It is estimated that if the electricity supply had been compromised, it would have taken up to 30 seconds to restore it, although Mr Hoare warned of a longer lasting "reputational hit".
This follows a BBC Radio 4 interview with head of the UK intelligence agency GCHQ Sir Iain Lobban, who explained that the country is being subjected to "industrial scale" cyber attacks.
He highlighted that criminals are going in search of intellectual property, which they then hope to be able to use for their own gain.
Sir Lobban warned that many of these threats go undetected by both victims and security organisations.