This is really funny and at the same time not funny cos I've heard same experience before here in Nigeria. Don't know this same thing has been happening in London as far back as 1972. Those guys are real scammers.

Here is my own story......
It happened to me 5years ago in the the ancient city of Ibadan, Nigeria. I was going home from I program I went for and I only had 2000naira on me.
When I got to iwo-road under the bridge, I saw a group of people gathered around the card man(dealer). He will just shuffle 3 cards (2 black and 1 red) and ask someone to pick the red. The deal was to double the amount put if one can pick the red.
I watched for some time and felt it was too easy to pick though I never wanted to use my Money. All of a sudden the card man pointed at me to pick the red and asks me to put 1000naira. As I was about to pick, he immediately asked me to increase the amount to 2000naira just before I touched the card which I initially refused but when he insisted, I gave in as I was so sure to pick the correct card.
I was so surprised when I picked the card and it was black. I couldn't believe and I felt I've been charmed or maybe the whole thing was magic. He asked me to go another round which I declined cos I had no money left on me and immediately they realised that I was not ready to stake any money again, they asked me to leave. That was when I knew the card man was not alone. Other people I met there that has been winning are to gather with him.
I refuse to leave and wanted to create a since when one mane called me aside and asked to leave the place before the gang up to beat me.
I have to trek back home that faithful day.

After one week, I saw those guys again and went there to watch them, that was when I discovered what they do. After asking you to pick, if they discover that your hand is going to the right place, they will look for what to use to distract you and change the card. That was exactly what they did when they asked me to increase my stake form 1000naira to 2000naira.

Well sorry @swissclive for what happened and thanks for sharing this for everybody to learn. I hope everybody has learned from this your post especially Nigerians cos I still see this people around