Britain could see its first full day without generating any electricity from coal on Friday, National Grid has said.
If the grid goes the whole of Friday without coal power, it would be the first continuous 24-hour coal-free period for Britain since use of the fossil fuel began.
National Grid's electricity control room tweeted: "It looks likely that today will be the first ever working day in Britain without coal since the industrial revolution!"
The electricity grid has been coal-free a number of times since last spring, as gas and renewables such as wind and solar play an increasing role in providing the country with power.
The longest continuous period until now was 19 hours - first achieved on a weekend last May, and matched on Thursday.
Coal has seen significant declines in recent years, accounting for just 9% of electricity generation in 2016, down from around 23% the year before, as coal plants closed or switched to burning biomass such as wood pellets.
The Government has pledged to phase out coal - the most polluting fossil fuel - from the system by 2025 as part of efforts to cut carbon emissions in the UK.
Hannah Martin, from Greenpeace UK, said: "The first day without coal in Britain since the Industrial Revolution marks a watershed in the energy transition.
"A decade ago, a day without coal would have been unimaginable, and in 10 years' time our energy system will have radically transformed again.
"It is a clear message to any new government that they should prioritise making the UK a world leader in clean, green technology.
"They will need to get on with the coal phase-out plan and recognise the economic potential of renewable energy and energy efficiency.
"We can meet the UK's needs for skilled jobs and fair bills, whilst also meeting our climate targets."
If Britain goes without coal for the whole day, it is thought it will be the first time it has been without electricity from coal since the world's first centralised public coal-fired generator opened at Holborn Viaduct in London, in 1882.
Industry body RenewableUK's executive director Emma Pinchbeck said: "The change in how we produce energy is the industrial revolution of this generation: as the age of coal passes, the renewables boom is well under way.
"Coal has been part of the UK's past, but we should celebrate the move away from dirty and old fashioned technology to a modern, clean energy future."
Juliet Davenport, chief executive of renewable electricity supplier Good Energy, said: "Moving away from big power stations burning old-fashioned sources of energy, towards local renewable forms of energy just makes common sense.
"Our energy is becoming cleaner and greener, with wind, solar and other renewables generating more of our electricity than ever before."
Environmental lawyers ClientEarth have used the milestone to call for infrastructure to support the changing energy system to prevent disruption as more decentralised, diverse and clean power comes online.
Chief executive James Thornton said: "Today is testament to clean energy's expanding role in the market and another reminder that we should not be fixating on natural gas as a stop-gap.
"The Government has signalled unequivocally that we are moving on from our toxic relationship with coal. But we will see the end of UK coal before the 2025 deadline and the Government must pave the way for the transformation."
He said coal would be pushed out of the market by a strong price on carbon pollution and a surge in clean technology, with companies developing efficiency, storage and smart technologies to regulate energy demand.
"Coal may have powered the Industrial Revolution but today's energy leaders are the low-carbon innovators. Clean energy visionaries will win the race," he added.