A special case of the ‘How much to order?’ decision in inventory control is the ‘Should we order any more at all?’ decision. Retailers especially need continually to review the stocked lines they keep on the shelves. For example, Marks & Spencer (M & S) has a simple philosophy: if it sells, restock it quickly and avoid stock-outs; if it doesn’t sell, get it off the shelves quickly and replace it with something which will sell. The M & S approach often means putting a new line on the shelves of a pilot store and watching customer reaction very closely. The store most often used for these trials is the company’s Marble Arch store in London. Sometimes it is possible to make a restocking decision within a few hours – not surprising when the time-frame for stock rotation can be as little as a week.