To use the mystique already surrounding Centurion to increase conversion rates. Was there a way to recreate the tantalising power of holding the Card without sending out actual cards?Our answer: an elegant black box with a Centurion Card, personalised with the recipient's name, inside. Their only obstacle? It was sealed inside a block of solid glass.The accompanying invitation acknowledged the rumours surrounding Centurion, and how tantalisingly close they were to experiencing what this rarefied world felt like.

One person described the effect of the mailing as "Like having a Ferrari in the driveway, but without the ignition key."

The response rate of 64% comfortably beat the ambitious target of 50%, and was well above that obtained in previous launches.

Anecdotally the reaction was also good. A group of prosperous Swedes spent an evening attempting to liberate the Card from its glass block. Many recipients were so taken with the glass encased Card that, when signing up, they asked for a matching block with a Card in the name of their wife or husband.