When Robin got home I checked the shopping list and asked him whether the fact that he hadn't crossed it off meant that he hadn't been able to get the toilet paper. He said that they hadn't had it and there hadn't even been a blank spot on the shelf where it should have been. Robin put away the chilled/frozen items and we then went out and collected Theo.
After we got back I started on putting away the dry goods. The things from Lidl were fine. In putting the other items away I discovered that the reason Robin had been unable to get the toilet paper was that instead of going to Sainsbury's in March he'd gone to Tesco! Not unreasonably Tesco don't stock Sainsbury's own brand recycled paper toilet paper!