23 Envelope was the name given to the graphic design partnership of graphic designer Vaughan Oliver and photographer/filmmaker Nigel Grierson from 1983-1988. During this time, they created a distinct visual identity for the British independent music label 4AD through their record sleeve designs for bands such as Cocteau Twins, Dead Can Dance, and This Mortal Coil.
As 23 Envelope, Oliver primarily art directed and designed, while Grierson primarily photographed (occasionally, however, duties would be exchanged and/or overlap). With Grierson's departure in 1988, Oliver saw fit to retire the 23 Envelope moniker, and continue working under the name v23 with new partner Chris Bigg, and various design associates that would come to include Paul McMenamin, Timothy O'Donnell, Martin Andersen and others.
A quote from a 2000 article on Grierson by Rick Poynor explains some of the early history of Oliver and Grierson:
Publications featuring the work of 23 Envelope
The work of 23 Envelope has been well-published in books and design magazines especially under Vaughan Oliver's name.