Sir, It is interesting that in an age when brands have so much customer information available, they can still make changes that upset consumers. Twinings and Heinz are just the latest in an honourable list of companies whose modifications to popular products have produced a backlash ('Twinings old Earl Grey back on sale (sort of)', 10 September).

Manufacturers today have to take into account many competing factors when they make decisions the retailer's requirements, competitor activity, regulatory demands and their own operational drivers. It is like skipping between preset stations on the radio, and the consumer's voice can easily fade out altogether. Brands need to tune into their customers and listen on a daily basis. Genuine, open listening to customers is too often a last resort when it should be the cornerstone of brand development.

Jonathan Salisbury, managing director, 100%Cotton