United Kingdom, July 16 -- Joaquin Phoenix has apologised to David Letterman for his infamous "horrible" appearance on The Late Show.

The 50-year-old actor memorably appeared on the 78-year-old broadcaster's talk show in 2009 to promote Two Lovers while in character for his mockumentary I'm Still Here -for which he had publicly announced he was giving up acting to focus on a hip-hop career - and he admitted he felt "stuck" because of his commitment to the project.

Appearing on The Late Show, which is now hosted by Stephen Colbert, this week, Joaquin recalled: "It was strange, because in some ways it was a success and it was also just one of the worst nights of my life.

"As part of the promotion for a film that I had made, I was coming ...