Sir Terry Pratchett: The author's legacy to research

Sir Terry Pratchett has died aged 66, having had Alzheimer's disease for eight years.

He was first diagnosed with Alzheimer's in 2007, but continued writing. He became a patron of Alzheimer's Research UK in 2008.

Tim Parry, from Alzheimer's Research UK, spoke to the BBC about the legacy the author had left behind.