Marks and Spencer, the UK retailer, last month ran a pre-Christmas “guerrilla sale”, reducing its prices by 20 per cent for a single day in an attempt to ignite demand among consumers. In the US, meanwhile, retailers including Wal-Mart, Neiman Marcus and Toys R Us stole a march on last month’s “Black Friday” discount day following Thanksgiving by promoting price cuts beforehand.

Early discounting is risky, however. Shoppers may hold off buying in expectation of further sales or discounts. Profit margins are squeezed. And deep or frequent discounting may damage the brand. Is it a sensible strategy for retailers, even in tough times?