It is fairly easy to see when someone is recording with a smartphone given how they hold it. I don't think this is the case with smart glasses. This is sometimes only made evident by a light on the glasses, which cannot always be seen, and not all smart glasses have.
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Whilst recording and sharing of personal data by smart glasses is covered by the Data Protection Act 2018, I think that new legislation should be introduced which specifically relates to preventing misuse of smart glasses, to prevent people from recording others without their knowledge.