Trivia: Dog makes a quote from Winston Churchill, and a reference is made by XXXX and Jimmy in Layer Cake. Matthew Vaugn, the producer of Lock, Stock is also the director of Layer Cake.
Trivia: Just after bacon orders '3 of your most refreshing drinks' listen to the football commentry being played in the background. The film's director Guy Richie is playing on the wing.
Trivia: Producer Matthew Vaughn makes a cameo as the yuppie whose car is stolen by Dog.
Chosen answer: If you are playing blind, you obviously aren't allowed to see your cards, nor exchange any cards. So if I'm playing open, I've seen my cards (and only me) and after the first round of betting I can exchange some or all of my cards. Statistically I'm now going to have a much greater chance of having a better hand than the blind man. Both players know who's likely to have the best hand, so it's a very brave gambler that plays blind for more than a couple of rounds. Imagine betting hundreds or thousands of pounds on cards that you haven't seen versus a hand that your opponent has managed look at and change. The rule an open man can't see a blind man tries to even up the odds, and make the game more interesting. It's literal seeing, rather than poker terminology.
They are playing 3 card brag. Nobody can exchange cards regardless of whether they see or not.