We've been reporting on the chances of Robert Downey Jr returning for Iron Man 4 all week, and, despite some speculation that Colin Farrell is waiting in the wings to take up the role of Tony Stark, it seems Downey Jr is going nowhere - providing Marvel has (a) a decent script and (b) a fat wallet. We know it has at least one of these.

Robert Downey JrRobert Downey Jr as Iron Man

The actor hinted at the necessity for both during an interview with Entertainment Weekly this week (but mainly money).

"It's down to Kevin [Feige, Marvel Studios president] and Ike [Perlmutter, CEO of Marvel Entertainment] and Disney to come to us with what the proposal is, and that's on us to agree or disagree. When things are going great, there's a lot of agreement... It's that thing of: Why give up the belt when it feels like you can barely get jabbed?"

It's no real secret that Downey Jr's strong relationship with Marvel is based on lots and lots of cold hard cash. Following the success of Iron Man in 2008, Downey Jr's agents renegotiated his deal so that he would profit from any future movies in which he played Iron Man - that included, of course, The Avengers. It was alleged - by Screen Rant and others - that the actor would receive as much as 5 to 7 per cent of the box-office gross and Downey Jr confirmed that figure during an interview with GQ.

Robert Downey Jr Iron Man 3Is Robert Downey Jr ready for Iron Man 4?

"Isn't that crazy?" he said. "They're so pissed. I can't believe it. I'm what's known as 'a strategic cost.'"

Unsurprisingly, after scoring a further $75 million for Iron Man 3, Downey Jr finished 2013 as the highest paid actor on the planet. He'll get 5 to 7 per cent of the gross from next year's Avengers: Age of Ultron - which will almost certainly be $50 million plus - and Iron Man 4 now looks a distinct possibility. 

Oh, and there's always another Sherlock Holmes movie if he wants it.