[andrewcooke]

but to some extent that's no different to the problem of having truecrypt (for example) installed on your computer - you have to explain that. of course, in the case of truecrypt you can have multiple (edit: hidden) volumes - i guess the equivalent here might be to have an "innocent" video that can be unencrypted. even then, though, it will be clear that the time isn't current, so if there is any "on" light, or disk activity on recording, that could be used as evidence that other data exist....