The government will simulate a shutdown of the national phone network next week in an exercise involving hundreds of government and industry players.
The exercise - codenamed "White Noise" - is designed to simulate a catastrophic nationwide communications failure, will take place over Wednesday 11 and Thursday 12 November.
It will be the first time the UK has conducted such a large scale exercise, Geoff Smith, the head of communications security in the Department for Business, told a Lords committee today.
White Noise will simulate a total national collapse of the traditional Public Switched Telephone Network. There will be no impact on those not involved in the exercise.
Such a scenario could be caused by a cyber or physical attack, or a natural disaster.
Officials will monitor the government's ability to respond in a coordinated way, including keeping Parliament and the public informed.
"We will learn whether we can respond in real time," Smith said.
Data and mobile communications will remain intact throughout the exercise.
"We'd be reduced to carrier pigeons and semaphore if we didn't have some form of communications," Smith explained.
He added that anticipation of White Noise in Whitehall had already prompted "a lot of thought and action" over the resilience of government communications and said "a lot of money" has been spent on private sector help preparing for the exercise.
Analysis of the response to White Noise will add momentum to efforts across government to strengthen the UK's communications infrastructure, Smith claimed.
He was appearing before the House of Lords EU Sub-Committee on Home Affairs. ®