The 50 year old, who plays supervillain Scarlett Overkill in the animated film, stunned in Stella MCCartney on the yellow carpet in London's Leicester Square, but she had to dash back to her hotel as everyone else settled in for the movie.

Bullock explains, "I went home and snuggled with the boy because he had been sick, so I wasn't gonna stay away any longer.

"I brought him some balloons and some Gummi Bears and we just made a little tent and snuggled."

Bullock admits her adopted five year old had a lot to do with the filming of the movie - as the crew had to work around his schedule.

She explains, "I said, 'If we're in L.A. we go to school and if we're in Austin (Texas) we go to school, drop off at nine and then I can be anywhere after that. And then I need to be out by a certain time to do the pick-up,' and they said, 'Fine'.

"They worked around little chunks around my schedule and it was brilliant."

Little Louis doesn't mind his mum working when he's at school but he hates it when she leaves to promote a movie or attend a film function: "He doesn't understand that but I say, 'I'm gonna get money for Legos'."