20 Pounds Ulster Bank

Ulster Bank Limited, a subsidiary of NatWest from 1917, occupied an unusual position in the British banking system — a Northern Irish commercial bank retaining full note-issuing rights while operating under the regulatory umbrella of a London clearing bank. The 1990 series came at a period of considerable political sensitivity around Northern Irish identity, and the bank's decision to maintain distinctly regional issues rather than deferring to NatWest branding was commercially deliberate.

De La Rue's security thread specification for this period was the early embedded metallic strip, predating the windowed thread technology that became standard later in the decade.