Britain’s biggest coal miner said production has been steady as it begins making progress on reducing its mammoth debt burden. The Doncaster-based group, which has been beset by mining problems in recent years, said production in the first three months of the year was “steady and in line with expectations” at 2.1 million tonnes, more than double the one million tonnes a year ago. Of this, 1.6 million tonnes was mined from its deep mines and 0.5 million tonnes was from its surface mines.