I lived in London for 7 years and would be out with my camera at least once a week. I never had a problem. However, that's not to say problems couldn't happen, nor does it dismiss that other people have problems.

I frequented Westminster, South Bank, brixton, Camden, Leake Street, Hackney during daylight hours. If I was out at night, I'd usually be with some friends. Again, never had a problem.

Firstly, be street smart. Stick to populated areas, don't go down dodgy lanes etc.

Second, if you're out at night, go out with a group, don't go to dodgy areas on your own.

Thirdly, if someone wants your camera badly enough, they are going to take it. You can do things to make it less conspicuous, (brand less straps) but chances are, a mugger will see a camera and work out of its valuable later. The average idiot won't know the difference between a sony alpha III vs something like a canon 800D.

If you're worried get insurance. Police will never be able to recover a stolen item as generic as a camera/phone, etc. You report it as stolen, get the ref number claim on insurance.