[quote:2a17b55f82="Pixel"]I think that there is still a crime under British law "Going equipped for a crime" - but which would be subject to interpretation - for instance, a professional locksmith might carry a set of lock-picks on the way to a job where he had to get someone into their house when they had locked themselves out and left their keys inside - perfectly legitimate - but someone [i:2a17b55f82]without[/i:2a17b55f82] that professional background, found with a set of lock-picks - especially at night - would almost certainly find themselves in court and convicted in very short order. There was a case many years ago when a someone - admittedly with a long criminal record - was convicted under this law because he had a sock in his pocket - judged to be usable to protect his hand when breaking a window to enter a house for the purpose of robbery.[/quote:2a17b55f82]

Having the tools would be physical proof that you were planning to commit a crime. It has to do with the level of evidence, as in talking about robbing a blank versus having detailed plans and safe-blowing supplies.

Regarding arrest: Police can arrest on probable cause that a crime has been committed. So they don't need hard evidence, but an actual crime has to be committed.

Conspiracy law requires evidence that more than one person agreed to commit the crime together, and in many jursidictions requires the commission of an overt act by at least one of the people (for example, if one of the people is found to possess a weapon.) It's also considered to be unjust by many people, so there would be political consequences (could be positive or negative) for anyone involved with having someone convicted on conspiracy charges.

edit: Two or more people planning a crime is different than one person planning a crime because once you start discussing the crime with other people and making plans with them, you're a step closer to carrying it out and it's harder to stop the process.