Shoppers love promotions – they capture new customers, get lapsed ones excited again and, crucially, can have an immediate and overwhelming impact on sales.

This Black Friday saw shoppers break an all-time record for transactions per second between 12pm and 1pm on November 25, according to data from Barclaycard. However, many multichannel retailers actually launched their Black Friday promotions well ahead of the day – some as early as November 4 – to “help consumers spread the cost of Christmas”.