Dennis St John was an actor.
300
Spartan Baby Inspector
Summer
Professor Ridley
Captive
Shoe Shine Man
The Aviator
Custodian
The Sign of Four
Sherman
Next Floor
Guest
The Greatest Game Ever Played
Wallis' Butler
The Long Winter
Lord Russell (uncredited)
I'm Not There
Captain Henry
The Minion
Gregor
P.T. Barnum
Beefeater
The List