They say women are safer than men when outside, less likely to be in fights and therefore safer.
I do feel a little 'on offer' wandering around certain places with my camera. I usually wear a long sleeved hooded top so I keep my hands inside the sleeves and therefore hide the camera.
When I took photos from Waterloo Bridge I was more worried about my bag being pinched as I took photographs.
I think you just have to be aware of your surroundings and it'll be ok.