You're never a true tourist in any of the cities in the UK, you're still in your home country, so you're highly unlikely to be a target.
These crimes almost always target foreign tourists quite specifically, they're far easier (and usually also individually more profitable) marks for a multitude of reasons.
I'v been a tourist in London several times (before moving there last year). Never had anything like this happen to me. No crazy Roma ladies trying to scam you. Worst you'll get is homeless people asking for some change.
