> In the UK and US at least, you do not need to show your photos to a person that tries to detain you, and you do not need to delete any photos. If you are arrested and charged with a crime, then they can inspect the photos as evidence, but not before. They still are not permitted to delete any.

My understanding is different for the UK. If you refuse to show a police officer the photos, they have the right to take you to a station, where they will examine the photos. Like you, i'm not a lawyer.

>Also, in the UK if someone who is not a police office tries to detain you (and this includes security guards and PCSOs), then they must be relying on the law of citizen's arrest, which means that they must have seen you in the act of committing an offense that could be tried at a crown court - in other words, something worthy of half a year or more in prison.

What you say is true about the citizens arrest, but as was mentioned in the article, my understanding was that they are able to call the police because you've been acting suspiciously, and that they have that 'right' to call the police if you are seen taking photos. They can't hold you, but then most people stay, because leaving is seen as an admission of guilt/being a terrorist. Would be nice if this was tested in a court of law, or to hear from someone who knows if it has. Even then i'm not convinced a Judge won't just say "Well, in this post 9/11 time, people should be expected to be stopped if they take photos of high value targets."

EDIT: Taking photos of a building == Acting suspiciously. Not what I believe, just what I understand is argued, often, when security guards call the police because you've been seen taking photos of their building.