Here we go again!
If you are on public land (the road, the pavement, the park etc.) you can take as many pictures as you like and no-one (repeat NO-ONE) has the authority to stop you. If however someone who appears in your images asks you to delete them you must do so, also if someone asks you not to include them or their family in your images, again, you must comply.
In privately owned property (like shopping malls) the rules are different. You can be restricted from taking pictures and if challenged, you must stop. No member of a security company or the Police has the right to insist you delete images and you cannot have your equipment confiscated unless you ignore instructions to stop taking pictures. The Police may
ASK you to delete some images, but only after they have inspected them and explained why they should be deleted. If you fail to do so you will be liable to arrest.
One final note of caution. On the pavement outside a building you will often find a row of brass studs, or a brass strip. This is the demarcation line and the building ownership extends to this point and you will be subject to the same rules as you would be inside the building.
99 times out of 100 if you have a friendly word with a security guard before you do anything most problems can be avoided. I once had a security guard escort me to the top of the Gherkin in London free-of-charge, and allowed me access to restricted areas to get better shots