The question might come down to this. Is consent broken if you are filmed without being asked first? or Is consent broken when *someone else* views the video without the person filmed being asked? (Simply, do you need to sign the consent first, or only if it is going to be seen by a third party?) I suspect that this is something that filmmakers have to tackle with should a bystander wander into their shot - have they just broken consent, or is it only broken if the bystander doesn't sign a release and you show it anyway? One for more legal minds than mine - and depending on your decision it might make CCTV cameras illegal...