The celebrity was in the British capital to do theatre work, when he was attacked Saturday after finishing his production.
Slater, 35, owes his life to his bodyguard that was accompanying him at the exit of the Gielgud Theatre.
According to Scotland Yard, "A 44-year old man was attacked by a knife which luckily did not penetrate his skin but only his clothes."
The weapon was found, and the police are pursuing the investigation.