I've worked for the company for 7 years, I know enough, and absolutely, safety over stock, but if you think that Tescos criteria for whether a store has a security guard in place is based purely on safety of the colleagues, then you're misinformed, it's a factor, but not the main one, if a store loses more in shrink from shoplifting than it costs to have a security guard employed, then that is the main factor, the guards don't print off training receipts, fill in the investigation books and submit them online through the companies intranet for nothing you know.