But what if he had won?

Neal Ascherson puts aside sentiment and looks at what Bonnie Prince Charlie really had to offer Britain

"THERE entered a tall youth of a most agreeable aspect in a plain black coat with a plain shirt not very clean ... he had black stockings and brass buckles on his shoes; at his first appearance I found my heart swell to my very throat."

A man grown old is remembering a moment in his boyhood. It was 23 July 1745, and young Clanranald had been taken on board the French warship Du Teillay anchored off South Uist. When he felt his heart swell, he did not yet know that the man with the not-very-clean shirt was Prince Charles Edward Stuart. That was the beginning, the first hours and days of the "Forty-Five" before the Prince had even reached the mainland and raised his standard at Glenfinnan. Three months before his victory at Prestonpans, nine months before Culloden.

In the late 1960s, when they took Peter Watkins's film Culloden around the village halls of the West Highlands, many in the audiences wept. Why did they cry, those people who normally hate to display emotion - and for whom? The film, true to its own times, presented the Prince as a callous, effeminate dandy. Perhaps they were simply weeping for themselves, for the loss of that distinct and confident Gaelic life which withered under the Hanoverian guns.

Yet the answer is not likely to be so simple. That Prince, worthless as he ultimately was, had a time when he could make others cast down everything to follow him. The audiences wept for an ancestral calamity, but also for the man who had made their fathers' hearts swell.

It is all so long ago now, that Hebridean summer day echoing with the calls of oyster-catchers and tern, when the smiling young man entered the cabin and was not recognised as the angel of death. Now the "Forty- Five", on its 250th anniversary, is a tourism resource and a Bonnie Prince's heritage trail. Not the English but the Scots themselves resolved long ago that the biggest, most dangerous and last of the Jacobite risings should be rendered harmless by immersion in sugar. Yet we still do not know what to make of it. Could the Prince have won? Should he have won?

A letter from Ireland arrived last week, with a stamp commemorating the Battle of Fontenoy, 1745. A few weeks before Prince Charles Edward arrived in the Hebrides, the French had inflicted a crushing defeat on the British - who were broken by the savage bravery of the exile Irish Brigade serving in the French army.

The Royal Mail, in contrast, has emphatically no plans to issue commemorative stamps for the "Forty-Five", far less for Culloden. That seems tactful. Still, the Irish stamp - a gorgeous little rectangle, like a memorial window, showing soldiers bowed before a Celtic cross with the battle raging in the background - is a reminder of why the Prince could not win. Fontenoy was too successful. The French threw the British out of Flanders, and in consequence found that they had far less need of a "second front" in distant Scotland.

The military help they gave to the Forty-Five was completely inadequate. That is the short reason for its failure. The Jacobites lacked field artillery and siege artillery, and never had enough cavalry to launch a serious charge. The French did supply a few guns. They transported not only the Prince and his staff but exiled Scottish and Irish units from their own army to Scotland. But none of this could compensate for the 10,000 French troops who originally had been earmarked for a landing in support of the Jacobites. As it was, the French at Fontenoy had inflicted a sort of "Dunkirk" on the British, driving off the Continent large forces which were then free to deal with an invasion from Scotland. In military terms, the Jacobite decision to turn back at Derby was correct.

The political "ifs" remain, none the less, and historians will always be tempted to play with them. The balance of military power in England was heavily against the Jacobites. But what about politics and public opinion?

People were terrified by the strangeness of the "Highland Army" as it tramped across Lancashire. There was neither readiness to join the Prince, nor enthusiasm to rally round the Hanoverian standard instead. But that sullen passivity weighed on the Hanoverian side of the scales. As an anonymous "English Gentleman" wrote afterwards, "the People preferred the lesser Evil to the greater, and by preferring Fools to Knaves, united to save the Nation".

King George II was packing to return to Hanover. The Duke of Newcastle, a senior minister, was on the edge of nervous breakdown, telling himself he ought to join the Prince but unable to take the plunge. Suppose the Jacobites had covered that last 125 miles from Derby to London - what then?

The school-book answer has for centuries been: fiasco.

There were not enough English Jacobites to support a new Stuart regime; Prince Charles Edward and his father were too silly and self-important to make the political system work for them; the English people would have risen sooner rather than later against a Stuart restoration which seemed to favour Popery, to endanger the gentry and to put Britain in the pocket of France. Today, 250 years on, that no longer seems to be the only possible answer.

Diana Preston, writing in the Sunday Telegraph, suggests that a Stuart victory might have transformed the British Empire. England, Scotland and - most importantly - Catholic Ireland would have become three formally independent kingdoms united under one crown. This in turn would have opened up London's relationship with the American colonies, making possible a far looser pattern of control which might have avoided the War of Independence.

But even if the New Stuarts had proved intolerable, Ms Preston thinks, their very fall would have been fruitful. By the end of the century, their authoritarian style might have infuriated the rising British middle class - not just a handful of radical intellectuals - into the mood for revolution.

These are wild, seditious thoughts to find in the Sunday Telegraph. I take Ms Preston to mean that the fall of the Bastille in 1789 might have touched off a great modernising revolution this side of the Channel as well. That would have probably turned Britain - the "British Union of Kingdoms" or whatever - into three republics, and endowed them with a vigor- ous rights-of-man political culture.

The Scottish historian Bruce Lenman wrote 10 years ago that "the Jacobite political programme was neither ignoble nor unreasonable. Had they triumphed, not only would religious toleration in the fullest sense have come much sooner to the British Isles, but the relations between the three ancient kingdoms of those islands might have been placed on a more equitable footing".

I like all this revision. At least it is a remedy to the "wrong but romantic" school, the condescending picture of Bonnie Prince Charlie as a lad born not to be King but to fail nobly. That picture allowed George IV to wear Highland dress over his flesh-coloured tights, and Victoria to say sentimentally that she was a Jacobite at heart.

Sorting out what the Forty-Five meant in Scotland is even more difficult than assessing it in British terms. Was the Forty-Five a war of Scotland against England or no more than a Scottish civil war between Highland and Lowland? Neither explanation is good enough.

The historian Michael Fry argued in the Herald last week that modern Scottish claims to the rising as an independence war are crass. The Prince promised to restore national independence, and the 1707 Union was still widely unpopular. But Fry sensibly insists that most of those who marched with the Prince did so out of loyalty to the legitimate Stuart dynasty rather than "to liberate Scotland".

And yet most Jacobite songs started to be written (by Burns, Hogg et al) some 50 years after Culloden and are still being churned out today (the Corries, Andie Hunter). But Jacobitism was as dead as a kipper by the 1790s, and it is not for the House of Stuart that hard laddies in the bars of Glasgow folk pubs are getting lumpy throats. Those songs appeal to national feeling, and at that gut level, immune to evidence, the Forty- Five remains a war for a free Scotland.

As for the "civil war" dimension, that gets more complicated with every new historian's essay. Once the Forty-Five seemed like the rebellion of the old against the new: Gaelic-speaking Highlanders against Lowlanders, feudal Scotland against bourgeois Scotland, Papists and authoritarians against Presbyterians and democrats.

It wasn't so simple. The clan chiefs who came out for the Prince included some of the leading modernisers, whereas the Catholic peasantry of Barra and South Uist stayed at home. Most of the Jacobite army was Highland, but the Prince's civilian support came largely from the Episcopalian north- east. The town middle classes were hostile to the Jacobites, and so were the Calvinist regions of Ayrshire and the south-west. But the landowning class - who effectively ran Scotland - were ambivalent, and simply gambled on the outcome.

The Royal Bank of Scotland has just published the diary of John Campbell, its chief executive in 1745. As the Jacobites approached Edinburgh, the bank moved all its cash into the Castle. But when the Prince captured the city, with only the Castle holding out, Campbell contrived to smuggle the gold and silver out again to the Jacobites: as a result, their army was paid and supplied and able to march on into England. And yet, unbelievably, Campbell kept his job after the Jacobite defeat. Other men were hanged for less. But he had friends, chancers like himself who had felt as he did, and it was all covered over.

In the muster roll of the Prince's army, the names are often followed by letters: K for "killed", T for "taken", EX for executed. A few, but very few, have KE for "turned King's Evidence". It is the roll of a losing side. Some are buried under that sinister mound at Culloden, but their cause is also buried under layers of fear, hindsight and sentimentality. Is it possible that the Jacobites were not reactionaries but revolutionaries, offering Britain a new royal road into the future?

I cannot believe that. By 1745, England was past the Stuarts, and Scotland, about to share a British Empire, was past the unreliable status of a Union of Crowns. But the Forty-Five did offer Britain a sudden, complete change of structure and ideology. A similar chance, more obviously modernising, came a century later with the Chartists. But no political rebellion since then has marched its troops as close as Derby.