The Flag Institute maintains and manages the national registry of United Kingdom flags and this flag complies with its strict UK Flag Registry criteria.

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Some say the term jack should only be used to refer to the flag when it's flown on a warship but according to the Flag Institute, which runs the UK flag registry, this is a relatively recent idea.

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And one -- British Prime Minister David Cameron -- even bestowed Bo, the first dog, with a bone-shaped chew toy adorned with a UK flag.

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