American Express developed the black 'Centurion Card' for their very best customers. It is so exclusive that you won't even find details of it on the American Express website. It's available through 'invitation only' and reputedly requires card spending of US$5,000 per month.

This kind of spending brings plenty of benefits, including a personal travel counselor to handle all travel needs, and a personal concierge to help with anything from special occasion planning and selecting ideal gifts, to locating unusual items.

James Bush, Senior Vice President of Consumer Marketing, said at the launch of the card: "We created the Centurion Card in response to customer research that identified a small but affluent group of cardmembers for whom individual attention and access to previously unavailable elite travel benefits was of great interest."

As part of the service American Express has, for example, arranged for a brass band to play outside a London flat on Valentine's Day and for European Cup football tickets to be hand delivered outside a stadium in Spain. In addition to this personal attention there is access to a wide range of travel and retail privileges.

Hence we need to know who is our top 5% of customers and are we doing enough to see their needs and maintain their loyalty.