Maybe they were going to pick up a child. And me personally I'd be far more concerned with the attitudes of some of Tesco's staff, especially those lurking around the self-service tills. Teso is in my opinion the WORST store for customer service; I've visited different locations multiple times, and every time there are staff who seem to think they are God's gift and treat customers like dirt. Tesco, if you actually WANT customers to enter your stores then it's a good idea to make them feel welcome - this isn't a Strangeways shower or visiting area, it's a shopping mall.
Does it really matter.. place appears almost deserted.