What kind of poker are they playing in "Lock, Stock and Two Smoking Barrels"?

In Lock, Stock and Two Smoking Barrels, what is the card game Eddie is playing with Harry the Hatchet? I always assumed it was a card game I’d never heard of, but then I read in several places that it was poker. They’re only using three cards and there are rules about how an “open man can’t see a blind man” and other rules that don’t sound like poker. Is it poker, and if so, what kind?

I think the game is called “Three-Card Brag.”

Three card brag

Not poker, then. Thanks. Sounds like an interesting game.