Forming part of the Chepstow War Memorial (see NPRN 419429) is a standard 10.5cm L45 calibre deck gun from the first World War U-boat UB91. The UB91's first commander was Wolfgang Hans Wertwig. It undertool 2 patrols sinking 2 merchant ships and 1 warship. Of the two losses caused by the U-boat in Welsh waters, the first was the US Coastguard Cutter TAMPA (131 lives lost) on 26 September 1918 (see NPRN 525557). The second was the Japanese cargo vessel, HIRANO MARU, on 4 October 1918 (see NPRN 274680). Both attacks took place in the Bristol Channel.
The uboat was surrendered at Harwich on 21 November 1918. In 1921, on its way to be broken up at Britton Ferry, it undertook goodwill visits to several Welsh ports, including Newport, Cardiff, Port Talbot, and Swansea (e.g. newspapers accounts in the Cambrian Leader 3 and 8 January 1919) under the command of Royal Navy's Lt Brooke.
Town Council minutes note that Chepstow was offered a naval gun to form part of its war memorial in March 1920. The Cenataph and gun were unveiled in January 1922 by Mrs Francis Smith, the sister of William Charles Williams who had been awarded a Victoria Cross posthumously for his bravery during the Gallipoli landings. On the day of his death, 25 April 1915, he had held onto a rope for over an hour securing lighters carrying troops being discharged from the HMS RIVER CLYDE. He had stood chest deep in water, under continuous fire until mortally wounded by a shell. His commander later described him as the bravest sailor he had ever met.

Maritime Officer, RCAHMW, August 2017.