Los Angeles - Idris Elba was devastated when he discovered his ex-girlfriend's child wasn't his.
The Luther actor admits the moment a paternity test confirmed his US-based ex - whom he dated for several years - had been lying to him about fathering the son he had always longed for was the most "tragic" time of his life.
He told GQ magazine: "It wasn't immediately obvious - well, it was, because he didn't look anything like me. But it wasn't immediately obvious what had gone down. The celebration of having a son - from a man's perspective, it's massive.
"To be given that and then have it taken away so harshly was like taking a full-on punch in the face. Pow!"
The British hunk isn't embarrassed about admitted he was duped, but has now moved on and won't make the same mistake again.
Idris said: "You know, the truth is, like, even admitting it, I'll probably get laughed at for the rest of my life. But it is just tragic, and it happened.
"But I wasn't knocked out. I stood right the fuck back up, and I ain't aiming to take another punch in the face ever again ... It happened to me. I moved on."
The 41-year-old star believes the heart-wrenching incident was a life lesson from karma because of his bad boy past.
Idris added: "I've not been an angel in my life, either - do you know what I'm saying? To a certain extent, what goes around comes around. But for me in the future, I'm about being comfortable. That's it.
"I was running with cats. I mean, I was DJing, but I was also pushing bags of weed; I was doing my work. I had to. I know that sounds corny, but this is the truth."