Saint George has been the patriot of Genova since at least 958. Genoa also had a banner displaying a cross since at latest 1018, possibly as early as 1011 indeed the saint had his own flag, the vexillum beati Georgii (first mentioned 1098), a red flag showing George and the dragon. A depiction of this flag is shown in the Genoese annals under the year 1057. The Genoese flag with the red cross was used alongside this "Saint George's flag", from at least 1088, known as the insignia cruxata comunis Janue ("cross ensign of the commune of Genoa").
The saint's flag was the city's main war flag, but the cross flag was used alongside it in the 1240s.
The Saint George's flag (i.e. the flag depicting the saint) remained the main flag of Genoa till today. The flag now known as the "St. George's Cross" seems to have replaced it as Genoa's main flag at some point during the 9th or 10th century.
The flag of England derives from the flag of Genoa.it was borrowed by the Doge to the british ships for the sole purpose of being identified when entering the Genoese ports during the crusaedes.
The flag was later taken by the british back to the city london and used by the latter as its ensign and flag under a sp copyriht rent agreement with the Doge.