In 1815, Mount Tambora in Indonesia erupted, impacting the weather throughout the world. The Year Without Summer imagines its impact on six separate lives, thousands of miles away. They include a fenland farm labourer, a soldier returning from Waterloo, author Mary Shelley and painter John Constable. Laura McMillan talks to author Guinevere Glasfurd about her ingenious and poetic novel, The Year Without Summer.