It sounds like an intellectual suicide mission: persuade the Irish that any good came of the British empire. No matter what has been written by Ireland's own `revisionist' historians, the collective memory of the empire in Ireland remains a bitter one.

The legacy of Ireland's colonisation by Englishmen and Scots in the 16th and 17th centuries continues to divide the island, breeding strains of terrorism, criminality and sectarian hatred which seem ineradicable.

Not even the most jingoistic Brit could deny that in the mid-1840s the British not only failed to alleviate, but actually exacerbated, one of the great catastrophes of the 19th century: the famine that killed around a million people.

The subsequent exodus of around six million Irish men, women and children -- an emigration larger in relative terms than any other in 19th century Europe -- is recalled in Ireland as a further tragic consequence of British rule.

When I visited Dublin last week it was not to whitewash the unquantifiable human suffering caused by plantation, famine and emigration. On the contrary, these are among the most lamentable debits on the balance sheet of empire.

Yet a balance sheet cannot be composed of debits alone. Tenaciously though hardline Irish nationalists may cling to the belief that nothing good ever came from east of the Irish Sea -- ex Britannia, nil salus -- it's the job of the historian to consider the credit side too, not least because it has important implications for the world in which we live today.

First, let me come clean. As a Glaswegian from a solidly Protestant background I grew up with memories of the empire that were diametrically opposite to the Irish nationalist view.

Scotland was North Britain, Glasgow the Second City of the Empire and without the Scottish regiments the English would have lost both world wars.

To someone of my generation, born the year before Winston Churchill's death, the world seemed to have been on the slide since the empire's decline and fall. As for Ireland, it was simply a failed Scotland.

Instead of a Protestant industrial south dominating a backward Catholic north, in Ireland it was the backward Catholic south that had the upper hand.

The Irish could have been Scotland; instead they had ended up being Poland.

One of the greatest joys of studying the past is that you get to ditch your youthful prejudices. The reality, as I came to understand when I began to study Irish history, was altogether different.

The union of Scotland and England was, from its outset, a partnership -- if an unequal one. The political union of crowns and parliaments was accompanied by a social union of aristocratic and commercial elites and, of course, a common adhesion to Protestantism (albeit different brands). The two peoples joined forces to pursue profit and power overseas.

The union of Ireland and England was another matter. It was achieved by conquest and colonisation; indeed, Ireland can justly be called the experimental laboratory of an Anglo-Scottish project to `plant' British culture in strategic overseas outposts.

Looking down on the Bogside from the walls of `Londonderry' -- there's no point calling those forbidding walls anything shorter -- I think I grasped for the first time the true nature of what was begun there in 1610.

The Irish were on the receiving end of a policy of expropriation and `ethnic cleansing' every bit as ruthless as that which would be attempted in North America.

The difference between Northern Ireland and Massachusetts was this: because the Irish were resistant to British diseases, they survived. The native Americans were less lucky. In Massachusetts they were almost entirely wiped out within decades of the Pilgrim Fathers' arrival.

The colonisation of Ireland brought misery in its train. Subsistence agriculture -- with any surplus pocketed by an alien landlord class -- condemned the Irish to grinding poverty and, ultimately, starvation.

In 1500 the average Briton's income had probably been about 45 per cent higher than the average Irishman's. By 1820 that gap had become a gulf: British incomes were nearly two-and-a-half times those in Ireland.

Instead of being Massachusetts, Ireland was fast becoming India.

Yet from 1850 onwards, things dramatically changed. There was a huge outflow of people from Ireland -- mainly to the United States, but also in large numbers to other parts of the empire: Australia, New Zealand and Canada.

Their journeys were dangerous and uncomfortable, no doubt. But the work of economic historians such as Kevin O'Rourke has shown conclusively that the net effect of the Irish exodus was positive -- not only for the emigrants, whose living standards in the New World rapidly overtook those in the British Isles, but also for those who stayed behind, whose wages rose as the population declined.

The dogmatic nationalists may not like to hear this, but the rate of growth of per capita gross domestic product (GDP) in Ireland was around a third higher than it was in Britain.

By 1913 Irish wages were rapidly closing the Anglo-Irish gap: a Dublin building worker was earning around 90 per cent of his London counterpart's pay.

Thanks to `Anglobalisation' -- that extraordinary integration of global markets for commodities, labour and capital that occurred under British leadership after 1850 -- Ireland experienced its first economic boom. It was Catholic peasants, not Anglo-Irish landlords, who benefited. The combination of falling grain prices and Liberal legislation to improve the lot of tenants meant that inequality within Ireland was significantly reduced.

So Ireland went from being little India to being little Canada -- part of a thriving Atlantic economy. The tragedy was that this economic convergence between Ireland and Britain was not accompanied by a simple political concession.

`Home Rule' had effectively been granted to Canada, Australia and New Zealand by the time Gladstone proposed restoring Dublin's own parliament and granting the Irish a degree of political autonomy. Yet unionists in Westminster and the north-east of Ireland doggedly opposed the idea. Anti-Irish and anti-Catholic prejudices combined to sabotage the only viable non-violent solution to the Irish question.

'But wait a minute,' comes the nationalist response. 'Look how well southern Ireland has done since gaining its independence from the Brits.'

The latest figures from the OECD suggest that Ireland's per capita GDP is now higher than Britain's. Far from Ireland being a failed Scotland, Scotland now looks distinctly like -- I hate to admit it -- a failed Ireland. And how could the Celtic tiger ever have emerged as long as it was being sat on by the British lion?

The trouble with this argument is that Ireland's prosperity is the fruit of barely ten years of economic success. For most of the period after partition the Free State/Republic performed dismally: growth was 20 per cent lower in Ireland between 1913 and 1950 than it was in Britain.

Only when the Irish re-embraced globalisation in the 1990s -- in other words, only when they reverted to the economically liberal policies the British had pioneered a century ago -- did they achieve their economic miracle.

It goes without saying that Ireland's recent riches are the fruit as much of economic dependence as of political independence: dependence, above all, on American capital and European subsidies.

Drawing up historical balance sheets is never easy. When it comes to British Ireland, it is especially hard. Even today, four centuries after the first plantations, the `Brits' are a long way from being forgiven for their sins.

Yet the Irish were not only victims of empire. As emigrants (and indeed as soldiers) they were also among the beneficiaries of Anglobalisation.

Professor Niall Ferguson was in Dublin last week to promote his book Empire: How Britain Made the Modern World, published by Penguin. His television series of the same name is broadcast on Channel 4 every Thursday at 9pm.