Sir: A key lesson retailers and brands should take away from Asda’s recent Price Guarantee woes is: never underestimate today’s consumer (‘Asda drops £15 cap on APG after sorting out online voucher ‘glitch”, 17 November).

Shoppers exploited a glitch to each claim vouchers worth hundreds of pounds. When Asda tried to close the loophole by imposing a £15 cap, complaints were made to the ASA and Asda had to remove it.

Why? Because the recession has led to emergence of ‘professional shoppers’ who make it their business to exploit such loopholes. And it’s no good trying to change the T&Cs after the fact - the ASA will conduct an investigation even if there is only one complaint.

I suspect Asda was caught out by a combination of cunning rivals who purposely dropped prices on a number of lines, and cunning shoppers.

Retailers and brands need to be more radical in their contingency planning. They need to think like a miscreant and look for glitches. Strong, clear and well-communicated T&Cs are vital, as are robust systems and processes and a tougher approach to investigating abuses. Prevention is better than cure.

Jeremy Stern, MD, PromoVeritas