On the run from a determined street enforcer, a young Londoner will do anything and everything to avoid capture but the enforcer has pledged to kill himself in the event of failure.
Still feeling slightly muddled; the focus shifts from the enforcer to the young londoner and back to enforcer. It just doesn’t “flow” as nice as one would hope. I’m not certain WHO your story is about.
Also, the way you’ve described the “young Londoner” … makes it sound like it could be any teen-to-twenty-year-old in London. As in, it sounds like you’re saying “When being chased by a determined street enforcer, just about anyone in the world will do anything to avoid capture.” It sounds like a general statement, not like you’re describing the actions of a specific character. As a follow on effect from this (the young Londoner being vaguely painted) it sounds like the protagonist of your story is the enforcer. I may be wrong, but isn’t your intent to make the young Londoner evading capture the protagonist?
The inclusion of the fact that the enforcer pledged to commit suicide in the event that he fails to kill his mark is superfluous, because (although interesting), the stakes don’t relate in any way to the goals or conflicts of the young Londoner.
I agree with much of what nicholasandrewhalls suggests; however, I would say that the suicide of the enforcer adds an important tension to the plot, one to which you should refer (should he be the main character), but perhaps more obliquely so that the reader is left feeling they know enough, but want more. So an alternate way to refer to it could be, “…with serious consequences should he fail” or something of that ilk.
In this iteration of the concept, once again, to my mind, the enforcer comes off as the character with the greater motivation, the more compelling situation. Why? Because the stakes of failure for the enforcer are higher: he must pay with his life. By invidious comparison, the young Londoner only has to elude capture.
Revised Logline (after a great deal of tears and heartache!): A penniless young Londoner steals a suitcase full of ‘dirty’ money and starts to realize he must give the money to a charitable cause to overcome a family stigma. But first he needs to defeat the fearsome street enforcer sent to track him down.