Robert Downey Jr has told how he likes to do his father-son bonding in the bath.

The Judge star is a massive fan of a good soak in the tub, revealing that's how he unwinds after work, and likes to have a long hot bath every day. But he also likes two-year-old son Exton to join him.

Robert said: "I like to take an Epsom salt bath but I also like to take baths with my son.

"We have very complex baths. It's about what toys are we bringing in or what are we going to watch on the iPad. Spongebob or Bubble Guppies or maybe football. Daddy wants to watch football."

The 49-year-old actor - who also has a 20-year-old son Indio from his first marriage and is expecting a daughter with current wife Susan Levin - explores father-son relationships in his new film.

The Iron Man star plays a big shot lawyer who returns home to his small town to help his estranged father, the town judge, played by Robert Duvall, in his time of need.

Robert said: "I think it depends on the day what kind of dad are you. Most people are self-obsessed and I think having kids gives you such an opportunity to not have to think about yourself all the time.

"The film's also about how you can be pulled into something as an obligation that turns into something else and you go, 'This is absolutely not something I can deal with', and then you go, 'OK, I'll deal with it a little bit', and you get sucked into it.

"And on the other side, you get something from it that you would never have gotten unless you'd let go of it a little bit and changed a little bit and try and understand rather than just have everyone understand you."