Crime & safety
A traveler's guide to safety in the U.K.: Pickpockets, scams, terrorism, and more
Random, violent crime rates are much lower in the U.K. (all of Europe, really) than in the United States. Murder is rare, and terrorism is more a scary bluff than harsh reality.
British big cities are, on the whole, safer than U.S. ones. Your two biggest worries should be pickpockets and the traffic—especially since it will be coming from the "wrong" direction (look BOTH ways before stepping of any curb), plus there are those kamikaze Euro-scooters that routinely go the wrong way up one-way streets and even drive on the sidewalks.
Take all this stuff with several grains of salt. Other than taking some sensible precautions against theft, you shouldn’t have to worry much about safety at all.
I gotta tell you, I have spent a total of about eight years living or traveling in Europe, and I've had far more instances of feeling distinctly unsafe in the course of my everyday life in New York City than I ever have anywhere in Europe (and the only time I've ever been mugged was in my hometown of Philadelphia).