Richard Attenborough was 18 in In Which We Serve when he played the character 'Young Stoker'.
That was over 82 years ago in 1942.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 2014 he died aged 91, starring in 94 films in his career, 93 of those after In Which We Serve was first released. If he were alive today he would be 100.
In In Which We Serve, I think Richard Attenborough looks: