Which will work so long as you've used a perfect system that can't be shown to have encrypted data by the boffins of GCHQ. Not a gamble I'd take. Remember if you've claimed there is no encrypted data and so refused to provide a key they'll only need to show that there is encrypted data and possibly that you own that computer (but if you've made the aforesaid denial I don't think they'd even need to do that, logically) - perhaps on seizing the computer an officer caught information displayed on screen on their video camera (used to record during raids) before you hit the power switch. Perhaps there's a snippet of something that can be extracted from a volatile memory buffer?

I don't fancy your chances. So you may as well not bother planning any terror attacks, kthnxbye