Do you have a cigarette? The listener will sense your question is asking him/her for a cigarette. But, if the listener is not a Native English speaker, the result may be different.

Why total stranger would offer you cigarette? If I remember in western countries like around 20-30% of population smokes. So the chances for you finding total stranger who would offer you cigarette just like that are quite slim. Plus I consider some total stranger coming to ask cigarette on the street quite rude.

^^ Either: "Do you have a light, please?" (Nobody is ever going to hand you their lighter, so don't even bother asking for that) Or. "Pardon me, do you have a smoke?" Either way, by the way, is a VERY bad way to introduce yourself. But that's not what you asked.

I'm not going to lecture you about the problems associated with smoking, since you probably are fully aware. So I'm going to answer your question as well as I can. But the likelihood of a total stranger offering you a cigarette in London (or elsewhere for that matter) is very very slim. I presume you know this and you want to ask for a lighter? In that case ' Could I please use your lighter for my cigarette' would be the correct way to ask. If however,you want to ask for cigarette you can say ' Would you please give me a cigarette I could smoke?'.

Good day, sir. I would like to smell vile and repellent, and stain my teeth yellow. I would like to leave ashes about, and risk fire and death. Could you help me, please?