In 1603, or there about, James fifth of Scotland inherited England and Ireland. A big moment for him, I guess. Three years later, on April the Twelfth, a decision was finally taken to give his empire a red, white and blue flag. Red for the cross of Saint Andrew, white for the cross of Saint George and Blue for the cross of Saint Patrick. This first Union Jack lasted until The Act of Union in 1800. A year later, to mark the occasion, the Union Jack was very slightly redesigned by a committee of imbeciles.
And I should add, for those curious about the fate of Wales, that ever since Llywellyn was out castled by the first King Edward, seven hundred years ago, Wales has had the distinction of belonging to the heir apparent of the reigning monarch of the United Kingdom of Great Britain and parts of Ireland. And, though I don't know quite why, it's worth remembering the first Queen Elizabeth and several of the Henry's were Welsh.
I prefer the first Union Jack, because there was no way a person could fly the first Union Jack upside down. The second Union Jack is an appalling complexity of geometry, obviously designed by nit-pickers and grammarians, about whom I cannot say any more, without further advancing into that part of frustration over which I have absolutely no control, and which has already been cruelly tested today by frost and foul thoughts from imagination..
But for those who might still be curious about what happened to the Welsh flag when James inherited both the English and the Irish, I believe it enough to suggest the Welsh flag has contained a dragon since the last great Pen Draig sent cavalry to terrify the Saxons, around five hundred AD. An event from the Arthurian Legend which we here in Kentucky often find ourselves celebrating in a sometimes widespread and spontaneous manner.