Widmark plays a very convincing small-timer, and he gets to show off - at one or two moments he's quite over the top, but still enjoyable. He manages to keep the character likeable, somewhere in between childish naivete and ruthless egomaniac. His character, Fabian, runs into trouble with pretty much everyone in a pretty small universe of the London underworld.
Favorite scenes: The wrestling match between the two brutes is amazing to watch, especially knowing that whatever the outcome might be, Fabian would have had it.
Another great scene is the exchange between Fabian and the night club owner that he tried to con out of money. (Actually, he is the only one, Fabian didn't con) - Best use of a drumkit in a scene, ever.
Good script to look at.