content: Section 5 of the Terrorism Act 2006 states -  Preparation of terrorist acts (1)A person commits an offence if, with the intention of— (a)committing acts of terrorism, or (b)assisting another to commit such acts, he engages in any conduct in preparation for giving effect to his intention. (2)It is irrelevant for the purposes of subsection (1) whether the intention and preparations relate to one or more particular acts of terrorism, acts of terrorism of a particular description or acts of terrorism generally. (3)A person guilty of an offence under this section shall be liable, on conviction on indictment, to imprisonment for life.  Source This basically means that if you are charged under the Terrorism Act 2006 and have done something, that is legal, but the end result of the action is terrorism, you can be charged for it. Therefore making something that isn't illegal, a chargable offence.