Pratchett presents film on Dignitas

The author Sir Terry Pratchett is to present a documentary about the last moments of a terminally ill man who travelled to the Dignitas assisted suicide clinic to end his life.

The BBC2 programme will show the writer, whose Discworld books have sold millions of copies, at the controversial clinic in Switzerland with the 71-year-old motor neurone disease sufferer, named only as Peter.

Sir Terry, who was diagnosed with a form of Alzheimer's disease in 2008, said: "I believe everybody possessed of a debilitating and incurable disease should be allowed to pick the hour of their death. And I wanted to know more about Dignitas in case I ever wanted to go there myself."

In the hour-long film, which will be broadcast in the summer, he compares how different countries deal with the issue.