As someone who worked on the tills in a supermarket in that period, I was expected to make sure the signature matched with the signature on the card. If it didn't, I asked for more ID - which I did regularly. If they couldn't produce it, then I called a supervisor and left them to make the decision. It's not just about checking for stolen card numbers (although our system did that automatically eventually) it's also about the staff processing the sale be vigilant. Given the tales we hear from the US of unsigned cards and people using other peoples cards (when there isn't chip and pin) that's stuff you just couldn't do here. The culture is different.