The Hamlet star portrayed German official Reinhard Heydrich in the Holocaust-themed TV movie, and he admits the sombre project left him battling the blues.

He tells Britain's The Guardian newspaper, "It led me into a depression, there’s no question about that... Of course it was meaningless and superficial in relation to the thing (Holocaust) itself."

And it isn't the only role that has given Branagh sleepless nights - he struggled with his emotions after playing the angst-ridden title detective character in TV series Wallander.

The 54 year old, who has portrayed Kurt Wallander since the U.K. crime show - an adaptation of Swedish novelist Henning Mankell's novels - launched in 2008, reveals it has put him in a "permanent, acceptable state of anxiety".