Flags of the United Kingdom

United Kingdom of Great Britain and Northern Ireland

Who & why: the Anglo-Irish Treaty of December 1921 gives twenty-six Irish counties dominion status as the Irish Free State from 6 December 1922; Northern Ireland's own Parliament exercises its treaty right to opt back into the UK within the first month, splitting the island for the first time in its history. The state's new name is only made official five years later, by the Royal and Parliamentary Titles Act 1927 — the practical territorial change is 1922, the formal renaming 1927.

What it represents: the flag itself does not change at all in 1922 — the same Union Flag fixed in 1801, with St Patrick's red diagonal still standing for Ireland, simply keeps flying, now representing Northern Ireland's continued place in the union rather than the whole island's.

United Kingdom of Great Britain and Ireland

Who & why: the 1798 Rebellion convinces the British government that a separate Irish Parliament is a standing security risk; the Act of Union 1800, in force from 1 January 1801, abolishes it outright and merges Ireland into Westminster. Catholic Emancipation, informally promised as part of the deal, is blocked by George III and not delivered until 1829 — a broken promise that shapes Irish politics for the rest of the century.

What it represents: the 1707 Union Flag gets a fourth element, St Patrick's red saltire, counter-changed with St Andrew's white diagonal to keep both visible — the exact design still flown today, one of the very few state flags never once redesigned in over two centuries.

Kingdom of Great Britain

Who & why: a century of shared monarchs finally becomes a shared government: the Acts of Union, in force from 1 May 1707, dissolve both the Scottish and English parliaments into one new Parliament of Great Britain at Westminster. Scotland keeps its own legal system, established Presbyterian church, and education system, all guaranteed by treaty — the merger driven as much by the financial wreckage of Scotland's failed Darien colonial scheme as by any shared vision.

What it represents: the 1606 combination flag, previously just one option among several and used mainly at sea, becomes Great Britain's official flag for the first time — a political merger finally catching up to a symbol that had existed for a century already.

Personal Union of England and Scotland (Union of the Crowns)

Who & why: Elizabeth I's death without an heir in March 1603 passes the English succession to her cousin James VI of Scotland, who becomes James I of England as well — one monarch, two kingdoms, each keeping its own parliament, law, and church. James's own bid to formally merge them as a single "Great Britain" is rejected by both parliaments in 1606–07 and goes nowhere for another century.

What it represents: James's 1606 royal proclamation combines St George's cross and St Andrew's saltire into a single flag for ships of both kingdoms at sea — the first Union Flag, but a decorative and naval convenience rather than a legal national flag, since no single nation yet existed for it to represent.

Kingdom of England (with Wales)

Who & why: St George's Cross comes into wide use around the time of Richard I's Third Crusade (1189–99) and is well established as England's flag by the 13th century. Edward I completes the military conquest of Wales in 1282–83, killing Llywelyn ap Gruffudd and formalizing English rule with the 1284 Statute of Rhuddlan — his own son becomes the first English Prince of Wales in 1301 — but Wales stays administratively distinct until Henry VIII's Laws in Wales Acts of 1535 and 1542 fully incorporate it, with English law, English-style counties, and its own seats at Westminster for the first time. The Wars of the Roses (1455–87) and the Tudor century that follows both play out under this same flag.

What it represents: a red cross on a white field, England's colours. Flags of the World and Wikipedia agree that the earliest reference to the cross of St George as an English emblem dates from the 1270s (a 1277 account roll), that a St George banner flew beside the royal banner by 1300, and that it became England's national flag in the 16th century; a Crusade-era or 1190s Genoa origin cannot be substantiated. The cross is still flown as England's flag and within the Union Flag; the page's claim that the design has never been altered was not checked.

Kingdom of England (Pre-heraldic era)

Who & why: Æthelstan, grandson of Alfred the Great, is traditionally recognized as the first king to rule all of England after his 927 conquest of Northumbria and the submission of the Welsh, Scottish, and Cornish rulers at Eamont Bridge. The kingdom survives Danish conquest (Cnut, from 1016), Norman conquest (William I's victory at Hastings, 1066, which replaces the Anglo-Saxon ruling elite but leaves the kingdom itself intact), and the disputed Anarchy of Stephen and Matilda (1135–53). Wales, meanwhile, remains a patchwork of independent native princedoms throughout — the strongest, Gwynedd, ruling in its own right with no English overlord yet in practice.

What it represents: no securely attested national flag survives from Anglo-Saxon or early Norman England; royal and personal devices existed (a golden dragon associated with Wessex among them) but nothing resembling a fixed territorial banner predates St George's Cross. Shown here honestly blank rather than invented.

Celtic Britain, Roman Britain & the Anglo-Saxon Settlement

Who & why: Iron Age Britain from roughly 800 BCE is home to independent Celtic tribes — the Catuvellauni, Iceni, Brigantes, and others — with their own hillforts, coinage, and warrior aristocracy, briefly visited but not conquered by Julius Caesar's expeditions of 55–54 BCE. Emperor Claudius's invasion in 43 CE begins nearly four centuries of Roman provincial rule, interrupted by revolts such as Boudica's in 60–61 CE, and marked by Emperor Hadrian's construction of his namesake wall from 122 CE to fix the empire's northern frontier. Rome withdraws its remaining troops around 410 CE as the western empire collapses; Angle, Saxon, and Jutish settlers then migrate in and found a shifting patchwork of small kingdoms — the "Heptarchy" — until Æthelstan unifies them into the Kingdom of England in 927.

What it represents: no flag in any modern sense existed across this span; Celtic tribes used coinage and metalwork devices, Roman legions carried standards such as the aquila, and early Anglo-Saxon kingdoms used personal and dynastic emblems rather than fixed national banners. Shown here honestly blank rather than invented.

World context: Hadrian's Wall, begun in 122 CE and stretching 73 miles coast to coast, ranks among the Roman Empire's great engineering works and is now a UNESCO World Heritage Site; Rome's withdrawal from Britain around 410 CE comes the same year Alaric's Visigoths sack Rome itself; and the Anglo-Saxon settlement that follows runs alongside the Byzantine Emperor Justinian's construction of Hagia Sophia in Constantinople (532–37 CE).