If I stole a load of money, that could potentially help terrorists – if I chose to give it to them. In the absence of any evidence that I was likely to do this, or that that was why I had stolen the money, the offences for which I could be arrested, detained and questioned would surely be those pertaining to theft, not terrorism.

If what I had stolen was instead information, those possible offences might conceivably extend to those to do with spying. But still not terrorism. In fact, if David...