United Kingdom has a moderate crime rate (about the same as France). Take precautions to avoid mugging, bag snatching and pickpocketing. Be particularly vigilant at airports, railway stations and crowded public gatherings. Do not leave valuables unattended.
It's recommended to follow security precautions like wearing a money belt, leaving valuables in your hotel room safe or well out of sight, securing your bag, staying vigilant in crowds and steering clear of commotions.