Robert Downey Jr. is dedicated to earning his brown sash in the martial art of Wing Chun and he is halfway there after eight years of the strict discipline.

The Sherlock Holmes star works out with his sifu whenever he can and insists he can at least boast he's a good apprentice.

The actor tells Men's Fitness magazine, "I'm testing for the brown sash next. I've been doing it for eight years and I am now just approaching the halfway mark, grading-wise, which is great.

"That is an apprenticeship. Doing something for a year or two and being a black belt, to me, is something else. I also respect it and I am sure you have to work for it, but an apprenticeship takes a very long time.

"I guess in another eight to 10 years, I might know what I'm doing."