It's a week now since the tragic news of Robin William's death reached us, and it's still something we are all struggling to get our heads around. Last week, we saw many tributes from America's late night talk show hosts but we had yet to hear from the one who knew him best.

David Letterman and Robin Williams went back forty years together from their days working alongside each other in The Comedy Store. He took it upon himself to devote ten minutes of his show last night to the star, lamenting the times they had together, including Letterman's rather odd but hilarious cameo in Mork and Mindy back in the day.

Robin Williams appeared on Letterman's show a whopping fifty times over his career and if you go to about the eight minute mark in the video below, you can watch a heartbreaking montage of some of those appearances.

Letterman finished by saying; "Beyond being a very talented man and a good friend and a gentleman, I’m sorry, like everyone else, I had no idea that the man was in pain, that the man was suffering. But what a guy, Robin Williams”