On Tuesday May 10th, Britain’s coal power plants were completely silent. Between midnight and 4am, not a single watt of British electricity came from coal. This hasn’t happened in 130 years.
This does not mean that the UK was 100% renewable, as has been seen recently in Portugal and several other countries. Rather the event was caused by a combination of cheaper gas, ever more efficient renewable energy, and the increased cost of carbon associate with the EU trading emission scheme. These have combined to make coal comparatively expensive.