Many Britons who backed Brexit believed - and believe still - that a U.K. 'freed' from 'Europe' would be able to recover and re-establish its historic destiny as an independent global trading nation.

I write to relieve an intellectual itch. I stumble across a hitherto neglected set of events, transformations, characters, or source materials from the past, and they nag at me until I make sense of them in words. But I also write to seduce and to make my readers think.

America is the proud possessor of the oldest extant written constitution in the world, which was for its time - 1787 - a highly innovative and important document.

Empire in the past was always a far harsher and much more accident-prone business than conventional history books imply. And the costs of these overseas invasions were borne not just by those on the receiving end but - frequently - by ordinary, vulnerable people among or associated with the invaders.

From the American Revolution right up to the Second World War, the U.S. was more likely to provoke suspicion among members of the British establishment than deferential approval. It was seen - with good cause - not just as a potential rival for empire, but also as dangerously egalitarian, worryingly innovatory, and excessively democratic.

From the very beginning, Americans have exhibited a taste for expansion, an appetite for empire. One of the fundamental reasons for this is very clear. Like every other western empire that has ever existed, Americans may claim to have inherited the mantle of ancient Rome.

In both British and American history, fervent imperialism has always coexisted with bouts of fierce isolationism.

In the past, Britons were scathing about the cruelties of the old Roman empire and the excesses of Catholic empire builders such as the Spanish and the French. They convinced themselves that their empire was different and benign because it rested on sea power and trade rather than on armies.

For good or for ill, Britain is in some respects moving away from a prime-ministerial system towards a presidential one. This is emphatically not, as is sometimes argued, simply a function of Tony Blair's personal ambition. The shift towards a more presidential style was already visible under Margaret Thatcher.

The immediate impact of British imperial free-trading was often the collapse of local indigenous industries which were in no position to compete, and a consequent destruction of livelihoods and communities.

Far from being aberrant and un-British, criticising a war in which our troops are actively engaged is a long-established parliamentary and political tradition.

If the U.S. and its allies can invade a weaker country on the excuse it is abetting terrorism, then why should not India, say, launch a pre-emptive strike against Pakistan on the self-same grounds?

London is not just an international financial centre: it is also one of the most ethnically diverse places on earth. Three hundred languages are represented within its boundaries, and - as is true of some other English cities - more than half of London's inhabitants describe themselves as non-white.

The 1857 uprising in India did not free the subcontinent, but it changed the way the British viewed and sought to govern it.

The Canadian risings of the 1830s obliged the men in London to think much harder about settler self-government.

Even at its most powerful, Britain always needed alliances with other European states. There would almost certainly have been no British victory at Waterloo, for instance, without the assistance of Prussia.

Of course the U.K., and its component parts, should seek out as many connections with as many parts of the world as is profitable and feasible. But to play any kind of global role effectively, the U.K. is likely always to require allies within its own continent, and far more enterprise needs devoting to this.

Responding to Britain's future challenges will require unceasing agility in seeking out new alliances and refurbishing old ones inside Europe, not just outside it.

In the U.S., highly selective renditions of its history have served in practice to impose blinkers on some of its citizens and catered to vested interests.

Although Britain has, since 1653, had nothing approaching a single, codified constitution, it did for a very long time possess a broad cult of constitutional writing. The Petition of Right of 1628, like the Bill of Rights of 1689, was a cherished text. So, most of all, was Magna Carta.

Modernity is a shifting entity, not easily defined. Exactly the same is true of empire.

For a very long time, loyalists were often left out of patriotic American histories of the revolution. Or they were caricatured as upper-class Tory reactionaries, or - rather like the Jacobites - made the subject only of nostalgic antiquarianism.

The United States was founded on a revolution that abolished the monarchy, aristocracy, titles and primogeniture. Britain may be able in the future to become a more equal and open society while retaining all of these things. But this has yet to be proved.

Had Barack Obama been obliged to take his degree at the University of Akron, say, it is doubtful that his progress would have been remotely as stellar.

One of the reasons why the personnel of U.S. politics are more diverse is that - unlike the U.K. - one can compete for the top job without spending long years, or any years, in the nation's legislature.

One knows something is important when the powers that be choose not to acknowledge it in public.

Conservative and Labour governments have arguably championed British rights in Brussels so ostentatiously in order to deflect public attention away from their deference to Washington.

Acts of violence against one's own countrymen that are legitimated by religion are not new. Nor have such acts been unique to Islam.

In the past, rulers led their troops into battle and, even in peacetime, called themselves fathers of their people. And modern politics retains abundant masculine rituals. Prime minister's question time in Britain, for instance, is a stylised duel and tournament redolent of testosterone.

Anyone who has spoken to experienced combat troops knows that they rarely brag about their exploits. Strong and silent is the preferred style.

Partly because women in the U.S. are better represented in the hierarchies, the culture wars over gender there have been particularly fierce.

Britain, like other European states, is not and never will again be in the top-world-power league, so its male leaders can afford to play subtler, more variegated roles. Leaders of the U.S. don't have that option.

The gulf between imperial ideals and empire on the ground has customarily proved disillusioning not only for colonial peoples but also for some in the occupying power.

A society that feels itself to be flourishing is likely to interpret everything that happens to its own advantage and in its own image. By contrast, a society that feels confused or in decline often converts any event - however innocuous - into a weapon of self-laceration.

I was in Boston, Massachusetts, when Princess Diana died.

America's soldiery, like its war dead, comes disproportionately from its southern states and from its aspiring poor - both white and black.

The children of politicians learn the allure and tricks of politics along with their alphabet. They inherit a network of useful contacts, and - if they're lucky - a name that confers instant voter recognition.

In 21st-century America, as in Georgian Britain, elections are raucous, flamboyant, flag-waving, expensive, and sometimes ramshackle things.

Transatlantic flights are unflattering. Hairstyles flop. Makeup melts away. Faces shrivel or swell from dehydration, and contact lenses give way to spectacles.

America's entire homeland security enterprise positively invites questions even as it strives to reassure.

The U.S. is the most benign great power we will see in our lifetimes, and it is important for global peace that its leaders continue to value being viewed as benign.

Thanksgiving is America's favourite holiday, and a brilliant piece of personal as well as patriotic calendrical invention.

Most national holidays in most countries rest on selective memories of the past.

'Captives' was a deliberate bridging exercise, an attempt to use detailed knowledge of what Britain was like on the inside, to reach a deeper, more variegated understanding of how its peoples experienced external adventures and aggression over a quarter of a millennium in four continents.

Governments should encourage and facilitate the teaching of history, but one does not want them to be able to dictate, for political or partisan reasons, what kind of history and interpretations are on offer to children.

I'm struck by how impressively John Elliott assimilated new work on early modern England and colonial America, as well as keeping abreast with his own Hispanic studies, so as to write his recent 'Empires of the Atlantic World.'

I don't even know if I'm British any more. I'm transatlantic, I'm European.

In the twentieth and twenty-first centuries, products and tastes developed in America have increasingly influenced lifestyles in Europe, whereas in previous centuries, it was generally the other way around.

Brussels and its multifarious networks provide member states not just with trading access but also a guarantee of regular encounters, negotiations, contacts, informants, and alliances.

Men and women do not live by bread alone. They also need sustaining ideas.