"As this subject has generated the largest post bag of any single subject in our history, however," Ashburner noted, "there is clearly such an appetite."

The Union Jack's history is closely intertwined with the U.K.'s history. After Elizabeth I died in 1603, her cousin, King James VI of Scotland, ascended to the English throne as James I of England. With Britain united under one king for the first time, James sought to symbolize his joint rule of the two countries with a new flag in 1606. The design placed the traditional English flag, known as the cross of Saint George, over the traditional Scottish flag, known as the cross of Saint Andrew.

England and Scotland remained independent countries with separate parliaments, royal courts, and flags until they fully merged under the Act of Union in 1707. Queen Anne then adopted James I's symbolic flag as the national banner of Great Britain. When Ireland merged with Britain in 1801 to form the modern United Kingdom, the British flag incorporated Ireland's cross of Saint Patrick to create the modern Union Jack. The flag's design did not change after Irish independence in the mid-20th century because Saint Patrick's cross still represents Northern Ireland, which remained part of the U.K.

The Union Jack doesn't represent everyone, though. England, Scotland, and Northern Ireland are included, but Wales, the fourth U.K. country, isn't. Because Wales was considered part of the English crown in 1606 (with the title "Prince of Wales" reserved for that crown's heir) after its annexation by England centuries earlier, neither James I's original design nor any subsequent design based on it bears any influence of the culturally distinct, Celtic-influenced territory.

British authorities granted Wales' red-dragon flag, or Y Ddraig Goch in Welsh, official status in 1959. But attempts to add Welsh symbolism to the Union Jack haven't succeeded; in 2007, a member of Parliament from Wales proposed adding the Welsh dragon to the flag, to no avail. Iconography could involve more than just the dragon: Like the U.K.'s other three countries, Wales has a patron saint, Saint David, and a black-and-gold flag to represent him.

If Scotland stays in the U.K., incorporating Wales into the British flag could be as simple as adding yellow borders.

Flag Institute

Without Scotland in the U.K., the proposals become more diverse. One of the most popular post-Scotland designs that the Flag Institute received takes the path of least resistance by swapping out Scotland's colors in the Union Jack with one of the colors from Saint David's cross.

Flag Institute

Adding both colors from Saint David's cross, as the design below did, really makes the flag pop.

Flag Institute

Integrating elements of the official Welsh flag seems like a tamer choice than adopting the vivid color scheme of Saint David's flag.

Flag Institute

Another proposed design would divide the flag into four quadrants, with Saint George's cross in two quadrants for England, Saint Patrick's cross in another quadrant for Northern Ireland, and the Welsh dragon in the final one.

Flag Institute

The quadrant-based design bears a resemblance to the Queen's royal standard, which also divides the heraldic symbols of each country into different quadrants. Some designers scrapped the country-based designs and instead drew upon royal influences. The one below superimposes the crown on the current royal standard.

Flag Institute

Another design inspired by the monarchy superimposes the royal coat of arms on a modified Union Jack. The floral wreath surrounding the coat of arms represents the monarch's various realms: white roses for England, thistles for Scotland, shamrocks for Ireland, maple leaves for Canada, and so forth.

Flag Institute

But perhaps the boldest design of all is John Yates's "United Britain," a unique take on the Union Jack's cross-based design that Ashburner calls "unlike any other flag currently in existence."

Flag Institute

The Union Jack occupies a special place in British society. In the U.K., the flag is only flown on certain government-designated days—a stark contrast with the United States, where flag-flying is ubiquitous. Protestant unionists in Northern Ireland controlled the Belfast City Council for years and flew the flag from city hall year-round. When Roman Catholic republicans gained control of the city council in early 2013, they reduced the number of days when the flag would be flown from 365 to the standard 18. The move triggered 40 days of violence and sectarian clashes between unionists and nationalists, reflecting the broader tensions that endured even after the Northern Irish peace process in the 1990s.

The flag's importance isn't just political, either. The Union Jack is emblematic of modern British culture and society worldwide. These days, it's emblazoned on corporate logos, foreign aid, rock guitars, and even sex symbols. Perhaps no flag other than America's is as instantly recognizable around the world as the Union Jack is. Will a new flag retain that power?

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