The flag of ?

You often see the flags of Cornwall (St Piran's Flag) or the Scottish Saltire either flying or displayed on the rear of cars, but you don't generally see this flag which is featured in my Blip.
I probably see it more often than other blippers, some of my fellow riders fly it alongside the 'In remembrance' and Union flags.
I know what it is, do you have any idea?
Spotted it nearing the end of this mornings walk with Jonty, extra is of Jonty grazing, or maybe just sniffing around for evidence of other dogs.