This document is a research essay accompanying Great British Cover-Ups: 60 Years of Selective Memory (2025), a conceptual art project examining the role of British commemorative postage stamps in shaping and managing national memory. Drawing on theories of banal nationalism and philately as a vehicle of state messaging, the essay analyses how official stamps operate through selection and omission, reinforcing institutional narratives while obscuring episodes of state violence, negligence, and denial. The text focuses on the project’s Witness Edition, in which UK Royal Mail commemorative stamps were reused to construct artist’s envelopes highlighting historical silences including the Windscale nuclear fire, Bloody Sunday, the contaminated blood scandal, Covid-19 PPE failures, and the Windrush deportations. Posted across the United Kingdom on Remembrance Sunday 2025 and subsequently sealed for ten years within The Archive of Selective Memory, the work reframes the postal system as a medium of distributed witness. This essay constitutes Part I: Witness and is deposited as a fixed archival document. Subsequent writings may extend the project but do not supersede this version.