On Sunday we had an evening of rum, sodomy and the lash. Last night it was followed by amputations without anaesthetic and gutters running with blood. Quite a bank holiday weekend. Certainly nobody can accuse Channel 4 of offering an airbrushed version of the Nelson bicentenary in its schedules this week.But Channel 4 is not alone in its preoccupation. The bookshops are groaning with new volumes on Trafalgar. Interest in the Royal Navy of Nelson's - and Jack Aubrey's - day is as strong as ever. The drumbeat of commemorative events is already difficult to ignore as October 21 nears. All of which provokes a large question: what, if anything, should we be celebrating on the 200th anniversary of the battle of Trafalgar?To many, of course, the answer is so self-evident as not to be worth further thought: Nelson was simply the brave and innovative commander whose death in a decisive battle against an aggressive enemy cemented his place as the emblematic British national hero. Merely to ask such a question is to run the risk of suspicion and derision in some quarters.Yet it is precisely because Nelson and Trafalgar are so iconic that it is worth examining them anew, in the light of modern needs. Nelson's war-torn Europe may seem light years from the peaceful, cooperative Europe of the 21st century - but Nelson is still the man carved in stone on top of our most famous national monument. Few of us are wholly resistant to his magic. Channel 4's coverage understands these complexities. And as Andrew Lambert, one of his best recent biographers, puts it: "Whatever it means to be British in the 21st century, Nelson is part of that identity."If that is right, which it is, then we need, as individuals and as a nation, to have a view about Nelson - and we need to know why we have that view. His story is more, much more, than a national heritage costume drama. We need to rise to the challenge of saying whether, how and why he fits into Britain today.This is not to belittle an indisputably remarkable man, whose death triggered almost unanimous national mourning and pride. Whatever else one can say about Nelson, he was a man who both lived up to his billing and who, in a very modern way, created it too. Remember, he was the national hero - title and all - in life before Trafalgar as well as in death afterwards. Death just made it more so.Nor is it to encourage those who want to judge him by our own standards rather than those of his own time. Nervertheless, an entirely proper historical argument against the celebration of Trafalgar is that the wrong side won. Nelson, after all, was waging war not just in defence of Britain, but in defence of reactionary and royalist Europe against not just France, but the democratic and republican ideals of the French revolution too.So would it have been such a terrible thing if Napoleon's planned invasion of Britain had taken place? More than a decade after Trafalgar, the fallen emperor explained to his doctor on St Helena what he had in mind in the summer of 1805."I would have hastened over my flotilla with 200,000 men, landed as near Chatham as possible and proceeded direct to London, where I calculated to arrive in four days from the time of my landing. I would have proclaimed a republic and the abolition of the nobility and the house of peers, the distribution of the property of such of the latter as opposed me among my partisans, liberty, equality and the sovereignty of the people."Bring it on, some will be tempted to say. Except that we would not have been offered the second half of Napoleon's scenario without the first. The reform would have been established, but it would only have been achieved at the point of a French bayonet. It was a package deal. And if there is one thing that the emperor actually achieved in the many countries on which he briefly imposed republican constitutions, it was to mobilise those countries to get rid of him so that they could govern themselves as free, rather than subject, peoples.A more historically accurate objection is that Trafalgar was not the victory we like to imagine. No, this is not some smart revisionist way of claiming that the French and Spanish actually won a battle they lost. But it is to say that Trafalgar was a victory in a different war to the one in the myth.It is at best arguable that Trafalgar saved Britain from invasion. In fact, Napoleon had turned his armies eastwards, against Austria and Russia, well before Nelson's finest hour. Decisive though it was, Trafalgar did little to alter the course of the Napoleonic wars. But it did mark the climax of the long-running 18th-century battle between Britain and France for global naval supremacy - what some have called the true first world war. "The major long-term strategic consequence of the battle was that Britain possessed an unchallenged supremacy on the seas for the best part of a century," write Tim Clayton and Phil Craig in their book on Trafalgar.So that makes Nelson not the man who saved the nation but the man who made the British empire possible - not a comfortable thought for many, and not intended to be. Except that here too there are subtle issues. Napoleon may have presented himself as a warrior on behalf of 18th-century Enlightenment values, albeit in an increasingly perverted form. But Nelson, like the Royal Navy of his day, was a child of the Enlightenment as well. Nelson's navy would never have been the success that it was without a belief both in science and in treating people well. Nelson's leadership was based, Lambert argues, "on love, not authority". And certainly, if there was one thing that everyone agrees about Nelson, it is that his officers and men - black as well as white - thought he was the embodiment of great leadership. It has gone down in history as "the Nelson touch".In the end we return to Nelson not because what he represents is easy to accept, but because what he represents is hard to accept; not just because he knew how to command but because he knew how to command in a fight. There is no getting away from it. Nelson was a war leader, not a business leader. His true greatness lay in the clarity with which he persuaded people to follow him into highly aggressive actions that went beyond the limit of what they thought possible - and then, when on their own, to continue to act consistently with the spirit of his plans. Today we would call it empowerment. But Trafalgar is the classic example of that.Two hundred years ago this week, as he spent his last days ashore, Nelson repeatedly spoke of achieving an "annihilating" victory over France. It is a terrible word. But at Trafalgar he made the word a reality. It has to be faced that this is where Nelson's genius lay. Very occasionally it is necessary to do dreadful things. When it is they need doing brilliantly. That was what Nelson achieved, above all others in this country's history. For some it makes him a criminal. For the rest it makes him a hero. Sometimes the line between the two is a fine one.