Ducky's ringtone is "Scotland the Brave".
In March 2021, the Royal Mail did indeed issue a set of 10 stamps depicting Camelot and the Arthurian legend, although different in appearance from those shown in this episode. According to an article by Denise McCarty on Linn's Stamp News, there were two previous issues of stamps, "...a set of four issued Sept. 3, 1985 (Scott 1115-1118), to mark the 500th anniversary of William Caxton's edition of Le Morte d'Arthur by Sir Thomas Mallory, and two stamps in the March 8, 2011, Magical Realms set of eight (2879, 2880)."