1. It was first devised in the early 17th century as a result of much work by English and Scottish heralds to come up with an acceptable merging of the English and Scottish flags following James VI of Scotland’s accession to the English throne as James I. It is, therefore, heraldically correct (as per the rules of heraldry, at no point do the red bits touch the blue bits) and predates the United Kingdom, which didn’t come into being until the 1707 Act of Union.
2. Despite what some people may think, the terms ‘Union Jack’ and ‘Union Flag’ are in fact interchangeable, partly due to their both being used to mean the same thing in a Parliamentary debate about the flag in 1908 (which was also the first time that it was officially referred to as the national flag).
3. There used to be a Scottish version in which the white saltire (diagonal cross) of St Andrew was superimposed over the red cross of St George. Groom is vague on when this stopped being used, but it was definitely before the 1801 Act of Union which added the red saltire of St Patrick (even so, it would’ve been nice to have seen a picture of said flag in the book – my one complaint was that some of the accompanying photos seem to have been chosen at random, and it could’ve done with a few more photos of the flags described therein).
4. There is no representation of Wales in the Union Jack because Wales was never a kingdom (England, Scotland and Ireland all were). This is also why the Welsh dragon doesn’t feature on the Royal coat-of-arms.
5. Naval uses aside, there are hardly any rules about exact sizes and proportions of the flag – which may help to explain why some manufacturers get the fimbriation (the proportion of the thickness of the white bits) wrong. This perhaps also explains the varying shades that have been used for the blue parts.
6. With the exception of the rules that concern flying it at sea, there are also hardly any rules governing what you can and can’t do with the Union Jack (in complete contrast to, say, the rules concerning the Stars and Stripes), which may help to explain why it became a style icon in the 1960s (see, for example, its use by The Who and in the movie The Italian Job – and this phenomenon probably explains why the Union Jack, not the Cross of St George, was used by England fans at the 1966 World Cup).
7. There are more verses to God Save the Queen than anyone thinks there are. Most of them, admittedly, are about what General Wade was going to do to Bonnie Prince Charlie when they met on the battlefield, the Jacobite Rebellion of 1745 being the context in which the song was composed as an anthem of loyalty to the Hanoverian dynasty (in the event, the Government troops were outflanked by the Jacobites, who marched down to Derby via Carlisle rather than Newcastle, which was where Wade was waiting for them; Wade was subsequently replaced by the Duke of Cumberland, whose troops thrashed the Jacobite army at Culloden).