Save for one war back in the middle ages, when England unsuccessfully attempted to conquer Scotland, the two nations remained on friendly terms. They were more than friendly, in fact, as the two willingly exchanged heads of state. Scotland’s King James VI and I, several generations descended from Henry VIII, became the first ruler of both countries (hence his double title), followed by every ruler after him until the Acts of Parliament formally united Scotland and England into a single nation.

On this day, April 12, in 1606, a royal decree called for the first flag of the United Kingdom, made by superimposing the Cross of St. George over the Irish Cross of St. Andrew.

The proclamation did not call the new flag the “Union Jack;” it simply referred to it as “the British flag” or “Flag of Britain.” A “Jack” was a flag flown on the bow of British ships, and it is thought that when the new “Union flag” replaced the old one, the two terms for it were merged. The first official use of the term “Jack” for the flag came in 1674, in a proclamation over “His Majesty’s Jack.”