The security tags on expensive goods such as clothes and CDs set off an alarm if people try to walk out of a shop without paying, even if the items are hidden in their bags. Until now, manufacture of the tags has been too expensive to include on a bag of crisps or a tin of beans but now there's a cheap way of printing metal directly onto the tags. Join Geoff Watts at the checkout in the first of a new series. Email: [email address removed]