Johnny Depp has finally finished filming a documentary about rock legend Keith Richards after four years of hard work.

The Hollywood actor is a longtime friend of the Rolling Stones legend, and even landed him a job playing his onscreen father in two Pirates of the Caribbean movies.

Depp has spent the last four years working on a film about Richards' life, and he has now revealed the project is complete.

He tells Britain's Event magazine, "I've been working on it for about four years now and we've just completed the filming. Actually, it's a little strange to call it a documentary, it's more an opportunity to experience Keith - as people don't get to see him because he's quite a mysterious being. Essentially it's Keith and I sitting around having a conversation and what it boils down to is his wisdom and his philosophy and his experiences - and that would be cut with footage of his life.

"I got him for five days about three years ago, and then in February I was with him for another five days and we continued from where we left off...

"I feel blessed that this guy, who has never done anything like this before, has put his trust in me and allowed him to document his life. In some way - and I'm not comparing myself to him - I feel like Alan Lomax (music documentarian)... Doing this with Keith and recording how he thinks and how he looks back at 50 years of fame is pretty fascinating."