Attractive Great Britain First Day Cover postmarked 14 March 1975 at Southampton. Features the large British Postcard Centenary 1870–1970 design on the left, and the Universal Postal Union commemorative stamp showing the P&O Packet Steamer (Peninsula 1888). Clear circular Southampton postmark. Addressed to Mrs A. Whitlock, Leeds, Yorks. Ideal for collectors of UPU history, maritime themes, P&O, or 1970s GB FDCs.