The risk here is probably different compared to previous outbreaks as the Delta is ripping across the UK doubling cases every 10 days, as they re commence the upward trend on the graphs again.
If people walk past each other in stores and pickup the Delta which is what went on in Myer here, then it will be seeding all over the city. We won’t really know for another week or two.
Masks indoors will prevent much of that. Delta is a prick of thing to contain once seeding commences.