Carbon paper was first invented in 1806 and used in typewriters before it was largely replaced by photocopying and then electronic mail. But officials have been advised to keep carbon paper on hand in Whitehall departments in case Britain is hit by blackouts that leave offices without power for days, according to three officials. “The idea is that you will have people running up and down Whitehall handing out copies of documents to colleagues in other departments or services, to keep people in touch,” one official said. “This is about addressing concerns about how the government will maintain communication with each other in the event of a crisis.” The use of carbon paper is one element of an exercise conducted in the past week in some departments to test how the government could continue to operate in the event of a crisis such as an energy blackout or nuclear war. Spiraling international gas prices since Russia’s invasion of Ukraine have sparked an energy crisis across Europe, prompting fears of shortages in the coming winter. Officials created a cross-government program called Yarrow 2021 to improve planning and resilience by central and local government and industry to deal with a national blackout. Officials insisted the plans existed before the Russian invasion of Ukraine. “This program predates these events,” said one. Since then, stress exercises have been held every four months to ensure “appropriate risk management and preparedness”. But officials admitted the wargaming exercises had taken on new urgency given the worsening energy crisis, which has seen household energy bills rise by 80 percent in a year. The government has drawn up what it calls a “reasonable” worst-case scenario that includes cold weather and lower energy imports from Norway, which sees the UK facing an electricity shortfall of up to a sixth of peak demand. Officials believe that if this were to happen, without rations, there could be days of energy blackouts in the depths of winter. Although Britain has its own natural gas reserves in the North Sea and is not dependent on Russian energy imports, it has relatively low levels of natural gas storage. Under the scenario, the government may have to activate emergency measures to conserve gas, according to an official. Downing Street insisted that “households, businesses and industry can be confident they will get the electricity and gas they need”. Liz Truss, the front-runner to win the Tory leadership contest, has ruled out a partial energy crunch this winter. But Gavin Barwell, the former Downing Street chief of staff, said it was “crazy” to rule out the possibility of restricting non-domestic use to protect vulnerable people. Rishi Sunak, Truss’ rival to become the next prime minister, has also said the government should not rule out the energy voucher. “A lot of European countries are looking at how we can all optimize our energy use, it makes sense to do as a country,” he said during the final leadership contests this week. A government spokesman said the cross-Whitehall exercise would ensure central government could respond effectively to a “wide range of extreme scenarios”, however unlikely. “The UK’s secure and diverse energy supplies will ensure that households, businesses and industry can be confident they can get the electricity and gas they need,” they said.