The 'Iron Man' star revealed in a reddit chat that another
Character that he would like to develop is Perry Mason, the crime solvind defence lawyer of Erle Stanley Gardner's book.
Guy Ritchie directed the two earlier Sherlock films, based on the stories of Arthur Conan Doyle.
"Yes, we have a 'Sherlock 3' in development. We want it to be the best of the series, so that's a pretty tall order. Also, Perry Mason is a property I'm looking forward to developing further, going back to the 1931 book series... similarly to what we did with the first 2 Sherlocks, mining the original material for things that are 'new'," he said.
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"Very impressed with Benedict. Such smart writing on that show. I have screen envy," the actor said.
However, it is still not clear whether the actor will suit up for 'Iron Man 4' as he went on to confirm the Marvel movie to Ellen DeGeneres only to deny it while making an appearance on David Letterman's chat show.
Downey Jr also clarified his earlier remark that he would do 'Iron Man 4' only when his friend Mel Gibson is given the directing job on it.