Oh, it's an interesting story, this one! It's actually the flag of Genoa https://en.wikipedia.org/wiki/Genoa#Flag

There's a fairly large community in the area descended from Genoans who fled to London when Napoleon invaded. Those Genoans brought their flags with them to prevent Napoleon from capturing them, to sort of say "you've got the land, but you'll never get Genoa". Their descendents today still fly those same historic flags each year on the day that their first ship landed in London

Also, of course, lying is a popular hobby on the internet