Scarlett Johansson admits keeping the plot of 'Avengers: Endgame' secret was ''traumatising''.

The 34-year-old actress - who plays Natalia Romanova aka Black Widow in the Marvel Cinematic Universe - readily admits it was ''stressful'' to not slip up and spill any spoilers about the highly-anticipated blockbuster.

Speaking to talkRADIO at a London fan event for 'Avengers: Endgame' on Wednesday night (10.04.19), she said: ''I am so excited to not have to keep these secrets anymore like I'm stressed out about it like it's traumatising.

''I literally will go home and lie awake at night and be like 'Am I good? Did I say anything? No we're good?'''

Chris Hemsworth - who plays Thor in the franchise - went on to explain that although cast members are only given parts of their scripts, they are able to read the full movie with ''lots of security'' around, however, he opted not to as he ''feels like a fan'' and wanted to watch the movie ''come together''.

He said: ''We only read out individual pieces of script - we could go and read the entire script if we wanted in a room with lots of security around and stuff. But I feel like a fan of the franchise ... so if you get to go to one of the premieres you see it all come together.''

Scarlett stunned on the red carpet at the event wearing a Tom Ford silk satin jacket featuring a asymmetrical cut out and plunging cut-out neckline paired with chic tuxedo trousers.

'Ant-Man' star Paul Rudd, also attended the event alongside the movie's directors Anthony and Joe Russo.