Re: Street Photography
It depends on where you are stood.
If you are on private property then the owners of that property are within their rights to prohibit photography.
With very few exceptions, if you are stood in a public place - you can take photos of anything that you can see, and that includes people. Even if your subject is on private property. What you CAN get into trouble for is what you do with those photos and any implications that your photos make. For example if you took a candid shot of 4 teenagers sat on a public bench - fine. If you then used that photo in a press article that said 1 in 4 teenagers is a drug user, you could be in for trouble.
Too many jobsworth security guards about that have little or no understanding of the law. I find it easier to just move on and photograph something else. But - on a few occasions when they've been particularly obnoxious I've persisted and only once have they called the Police only to be told to stop wasting Police time. I was once stopped by the Police in Manchester and asked what I was doing. I explained about documentary street photography and they were fine.
Another point to note is that nobody can demand to see the photos on your camera or demand you delete them. They could get a court warrant to confiscate your camera but they'd have to be damned sure you were behaving in a way as to prepare for or facilitate a crime.
I was once yelled at by a PCSO because she just happened to be in a street scene I was photographing. She demanded I delete the photograph because she said it was illegal to photograph the Police on duty. So I then asked if I'd committed a crime. She said yes, I had committed a crime. I then asked her to clarify that she was asking me to delete the evidence of a crime. I think her tiny brain blew a fuse at that point and she wandered off. They are a lot better informed these days thankfully!