Peter Ustinov was 18 in After Mein Kampf when he played the character 'Marinus van der Lubbe'.
That was over 84 years ago in 1940.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 2004 he died aged 83, starring in 107 films in his career, 105 of those after After Mein Kampf was first released. If he were alive today he would be 103.
In After Mein Kampf, I think Peter Ustinov looks: