Britain went a full day without using coal to generate power, reports the BBC. It's the first 24-hour period of inactivity there since 1882, when the world's first public coal-fired power plant was stoked at Holborn Viaduct in London.
But Ms O'Hara says that while the country makes the transition to a low carbon system, coal remains an important source of energy.
According to Gridwatch.co.uk, around half of British energy on Friday came from natural gas, with about a quarter coming from nuclear plants.
Wind, biomass, and imported energy were also used.
As in the U.S., coal power's been squeezed out by natural gas, a cleaner fossil fuel, though the trend is now toward renewable sources. Britain will close its coal-fired power plants down for good in 2025, supposedly.