I used to be a bridge tournament director, and have spent a bunch of time working out interesting ways of cheating (which is quite easy, given that very little

I used to be a bridge tournament director, and have spent a bunch of time working out interesting ways of cheating (which is quite easy, given that very little information needs to be passed for a good player to have a massive advantage). My favourite 'famous' method of cheating reveals the number of Hearts in hand (mod 4) by the number of fingers visible in front of the fan of cards. My favourite 'own' method relies on colour differences between similar packs of cards. I discovered a couple of packs of the club's cards had been dropped and reassembled into complete packs but making the subtle difference in the blue colour on the back obvious. If you did that deliberately, with all the hearts swapped between the two packs, you'd have a complete read of heart length in all four hands, which would make life much easier. Wouldn't even need a confederate partner, and if it was discovered nobody would know it was you...