Filming polar bears in their Arctic home requires bravery and patience. Of all the wildlife film-makers who bring images of the natural world to our TV screens, few were as courageous or boundlessly patient as Doug Allan, who would spend weeks, even months on end in this harsh environment in order to capture unique and astounding footage. His long list of credits features many of the classic television series that have captivated audiences over the past few decades, including Life in the Freezer (1993), The Blue Planet (2001), Planet Earth (2006) and Frozen Planet (2011). Doug, who has died aged 74 of a brain haemorrhage in Nepal while heading for base camp at Annapurna, was particularly admired for his work in two of the world’s toughest environments: the polar regions and beneath the ocean’s surface.…