The motto in Latin is "Impiger et acer" - 'Energetic and keen'. Since the late 1920s, the squadron marking has been three (red) Xs (XXX). Since this closely resembles the Roman numeral for "29" (XXIX) there is a belief among current squadron personnel that this originated as a "misspelling" of the Roman numeral. Although various versions of the tradition are put forward, the most common explanation is that a mis-understood instruction to ground crew to paint "2 X's in front of the roundel and IX behind it" meaning "X,X,(roundel), and 'IX' or 'one-X'" resulted in "XX(roundel)'one times' X". In fact, the marking was always applied as "XXX(roundel)XXX" or as "XXX(roundel)" on smaller types, such as Siskins. It seems probable that the original adoption of "XXX" for the 1930s squadron marking was nothing to do with Roman numerals, but was a reference to the brewers' mark for "extra strong", frequently applied to kegs of beer, and that it is only a coincidence that this resembles the numeral for "29" (XXIX).