The high street flopperoo that was ‘Black Friday’ may have something to do with terrorism fears, or even the downturn of the Chinese economy: in last year’s ugly scenes of bargain-hunters wrestling over televisions, Chinese tiger–shoppers seemed to win most of the spoils. But this year you could have held a picnic in the entrance of an Oxford Street store without fear of being trampled; trade had migrated massively online, where total UK sales are estimated to have passed £1 billion in a day for the first time and to have peaked (how sad is this?) between midnight and one in...