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This is a major node of discussion in British history – so much so that it’s a perennial question during PhD comprehensive examinations, and such a staple of history essays that a mod brought the hammer down!

Answers range from ‘not at all’ to ‘very significant indeed.’ John Robert Seeley wrote, while the empire was nearing its height, “"we seem, as it were, to have conquered half the world in a fit of absence of mind." Even a century before him, Adam Smith claimed the empire was not empire, “but the project of an empire.” What they meant was that even the policy-makers and political leaders themselves didn’t see the development of an empire as a central aim of British policy, let alone identity. Taking a cue (and a pithy phrase) from Seeley, historian Bernard Porter has argued that any impact of the empire on 19th-century British culture was at best scattered and superficial. After all, such arguments go, most Political and cultural issues were not driven by Imperial issues: chartism was driven by domestic politics; how often did Jane Austen refer to imperial matters? If anything, the struggle for a common British identity took place on a more limited geographic scale, defined as much by wars against France and geographic insularity as by some sense of world-spanning empire. Indeed, Protestantism remained perhaps the strongest driver of common British identity well into the 19th century.

However, quite a few historians argue differently. Post-colonial theory and post-colonial history suggest that not only do we need to insert the history of empire into our histories of Britain, they are completely intertwined and we cannot understand one without the other. A very good example is Catherine Hall’s work; she suggests that accounts of colonial people hardened racial identities at home; Britons were made civilized in contrast with those savages, and to understand the identity of someone in Birmingham you need to understand his own imagining of someone in Jamaica. And indeed, given the extent to which the 19th century british industrial economy was built on imperial interconnections, it might be unsurprising that culture would follow suit. Take London, a city whose economy, architecture, and identity were all reconfigured by its status as an imperial capitol. When infantrymen in red or Khaki marched down the Kingsway before heading off to fight the Boers, it certainly had a hand in forging British identity and pride.

My own sense is that, especially in the latter half of the 19th century when empire was more celebrated, it did become a more central element in the making of British identity. Take the poems of Kipling, say, describing dominion over palm and pine. It was a move very much infused by the racial thought of the period; Charles Wentworth Dilke’s Greater Britain saw a union between the anglo-saxon, English-speaking countries of the world that united them with a common identity.

But at the same time, efforts to foster a sense of empire as a component of British identity strengthened at precisely the moment the empire itself began to falter. During the world wars, Britain called on its empire not only for men and resources, but as a source of propaganda—the NZ contribution to the war was minute in terms of manpower, yet here was a colony on the opposite side of the world with a common language, loyalty, and history to join the fight. The metropolitan government made every effort to play up a common imperial identity even as the dominions drew further away; take the 1924 Empire Exhibition, for example, which took place just before the Balfour declaration declared the dominions of equal status with the UK.

Hope that’s helpful?