Supermarkets continue to make money from shoppers who assume that bigger packs = better value, without actually working it out.

Asda have sold packs of 12 Andrex toilet rolls labelled “GREAT VALUE” while their packs of 4 were less per roll, according to Which? researchers. And the writer’s own local Asda were recently selling 750gm gammon roasting joints for £4.50 (£6 a kilo), 1.4 kilo joints for £6.00 (£4.30 a kilo) and 2 kilo joints for £10 (£5 a kilo), making the middle weight the best buy.