Robert Downey Jr. has ''missed'' his son ''a lot'' while promoting 'Avengers Assemble'.

The 47-year-old actor - who already has son Indio, 18, with ex-wife Deborah Falconer - and his spouse Susan Levin welcomed baby Exton Elias into the world two months ago, and he loves being around his ''really cute'' little one, but wishes he could have spent more time with him since his birth.

He told BANG Showbiz: ''I love being a father again, it's brilliant. Exton's really cute and I miss him a lot.''

Despite having an 18-year gap since he last welcomed a child into the world, Robert - who portrays Iron Man in the Marvel superhero movie - still employs the same methods he used when he became a dad for the first time to Indio.

Speaking at the European Premiere of 'Avengers Assemble' at Westfield London's Vue Cinema last night (19.04.12), he added: ''Fatherhood doesn't seem to have changed for me. With Exton, it wasn't really different to the last time, just the same. It's great.''

Robert was joined at the glitzy event by his fellow 'Avengers Assemble' cast members Scarlett Johansson, Mark Ruffalo, Chris Hemsworth and Jeremy Renner.