You can write the story of the Union Jack on the back of an envelope. The cross of St George, which stands for England and its principality, Wales, was in 1606 interlaced with the Scottish saltire (a saltire is a cross with diagonal bars of equal length) of St Andrew to act as a common flag for the two kingdoms united under the crown of James VI of Scotland, who later became James I of England. When Ireland joined the Union in 1801, the red saltire of St Patrick was added, offset or ‘counter-changed’. Hence, in the upper corner nearest the flagpole (the canton), the broad white diagonal should always lie above the red diagonal, unless the flag is being flown upside-down to indicate distress.

Saint George's early reputation was as a 'megalomartyr'

Nick Groom’s book begins in Roman times with tattoos, which were the insignia worn by the Ancient Britons. Attention then focuses on the dragon standard as an early emblem of union in the popular imagination – most famously as the golden dragon of Wessex. The dragon standard fell at the Battle of Hastings in 1066, but was carried into battle by English armies until the 15th century. It was flown alongside increasingly elaborate heraldic devices, which form what is essentially the ‘prehistory’ the Union Jack. Heraldry developed as a visual sign system to identify one’s family and lineage.

The three crouching lions were established by Richard the Lionheart as the royal arms of England. They were then ‘quartered’ with the fleurs-de-lys of France to indicate the English claim to the French throne – a claim that was part of the British royal title until as late as 1801. The harp of Ireland became part of the royal coat of arms when Henry VIII declared himself ‘King of Ireland’, and the red lion of Scotland was, of course, added by James. All of these national emblems remain in extensive use today: for example, as the three lions on England’s football jerseys and cricket sweaters.

Alongside the fantastical world of heraldry, the crosses of the three patron saints each have their own story. The bloody cross of St George was associated with the saint because of his early status as a ‘megalomartyr’. Long before the episode with the dragon entered his legend, he was depicted as a martyr among martyrs, tortured and executed only to be resurrected and come back for more, eventually being crucified. The St Andrew’s cross, a silver saltire on blue allegedly represented the diagonal cross on which St Andrew died, but it was also the omen seen in the sky by the Pictish king Angus before he defeated a Danish invasion. The case of St Patrick is somewhat different: his red saltire derived from a badge of the Geraldines, ancient kings of Ireland, that by the 16th century was being used by the Earls of Kildare to rally the Irish in rebellion against the English. Come the 1801 Act of Union and the need for the second Union flag – the one familiar today – it was apparent that the cross of St Patrick could be readily assimilated into the interlaced design of St George and St Andrew.

By the 20th century, the Union Jack had become a design classic

In the 19th century, the Union Jack became a globally recognised symbol for trade, colonialism, and the values of the British Empire. Unusually for a national flag, there were never any official stipulations regarding the dimensions, or even colours of the flag, and it is only at sea that there is any sustained respect given to its fabric. Neither are there restrictions on the use of the flag by private citizens. Since the 1840s, there have been Union Jack handkerchiefs and Harrods has been using Union Jack wrapping paper. It was both a sacred symbol – flying defiantly, for example, for three months over besieged Lucknow during the Indian Mutiny in 1857 – and a household knick-knack. Dozens of music hall songs were sung (Groom’s favourite being ‘My Girl’s a Union Jack Girl’, which compares the attractions of a young lady to the colours of the flag), there were Union Jack marches and polkas, and it was used to advertise anything that could reasonably be described as British.

By the 20th century, the flag had become a design classic. Although its totemic significance continued throughout two world wars, it was also a domestic commodity. In the 1950s, questions were asked in the House about the suitability of ‘Coronation ladies underwear, ornamented with the Union jack at the rear’. Commentators pointed out that the American Stars and Stripes was protected by laws regarding the desecration of flags, but not so the Union Jack. It became a Carnaby Street favourite: Mods wore jackets made out of Union Jacks, and a decade later punks were cutting up the flag and rearranging it. Since then, the flag has been flown by Freddie Mercury, the Spice Girls, and Iron Maiden. And it continues to be reinvented as a fashion icon: a trip down any High Street will reveal dozens of instances of Union Jack design.

Despite attempts in the 1970s to appropriate the flag as a right wing banner, the Union Jack now seems more firmly established than ever at the heart of British culture. The announcement of the successful London Olympic bid, immediately followed by the London bombings, was symbolised by the waving of flags one day, and the same flags at half-mast the next – a powerful example of the ability of a multi-coloured piece of material to express the feelings of the country. Indeed, the bombings led to a national debate on being British, a debate that will continue for years to come. Groom hopes that his book will contribute to that debate by suggesting that the ability of the national flag to keep changing in response to shifts in national identity – rather than being treated as a static, inert museum artifact – is itself characteristic of flexibility, contingency and compromise, values that we will need to cultivate in facing the challenges of the twenty-first century.

The Union Jack: A History of the British Flag will be published by Atlantic Books on 12 April 2006.

Nick Groom/English