Nelson’s brief trip ashore and visit to Merton was the first time he had set foot on dry land since rejoining HMS Victory upon his recall to duty in May 1803.

Given his continuing infatuation with Emma and his absolute adoration of his small daughter, Horatia, that may seem strange to us, unless we consider the facts - for the majority of that period, Nelson had been at sea and his periods back in English ports - principally Portsmouth - had been necessarily brief.

On top of that, we must not forget that he was seldom in the best of health these days and had but one arm - in those days before the introduction of access stairways while in harbour, it was a case of climbing a rope ladder, or else being lowered and raised on a form of breeches buoy, something the somewhat arrogant Horatio considered beneath the dignity of an admiral in the Royal Navy.

Besides which, with his fame and rank, his attitude was that other people could come to him - it not only saved him trying to get up and down a ladder with only one arm, it also saved him a lot of time and he could see more people and get more done that way.

And Nelson knew that there was much to be done - the force he commanded was inferior in size and firepower to that of the Franco-Spanish allied fleet and, whilst he believed that his men were better sailors and more efficient gunners, it was essential to keep every crew on top form.

His big problem was that Villeneuve was safely moored in Cadiz, whose defences had been greatly improved since the days when Drake sent in his fireships and “singed the King of Spain’s beard”, which precluded any form of direct attack.

Not that Nelson especially needed to draw Villeneuve out - since Copenhagen, Napoleon was coming under increasing threat from the north and especially from Russia and Admiral Calder’s partial success at Cape Finisterre would only encourage France’s enemies in that area.

The army intended for the invasion of England could not be held in position indefinitely, as much of it would be needed for any northern and eastern campaign against the Tsar’s huge forces, but the Armie d’Angleterre could not attempt to crush the Channel without overwhelming naval support.

The longer Villeneuve dallied in Cadiz, the less chance there was of any invasion and every commander on both sides was well aware of this, especially Nelson - except that commanding a simple blockading operation wasn’t quite his thing ...

Villeneuve, on the other hand, was between a rock and a hard place - even though he knew Nelson was by far the better commander and even though he knew Cadiz was just about impregnable, he also knew that he couldn’t just sit tight and wait.

Not only was Napoleon sending him orders, urging him to break out and engage the British, he knew that he needed to do something to salvage his battered reputation, following a year of unmitigated failure.

His trans-Atlantic foray had been intended to draw off British military resources, both naval and military, firstly by landing troops to capture British assets in the West Indies - destroying them and then leaving, if necessary - and then, having avoided Nelson on the return journey, to put more troops ashore in Ireland, where an uprising would occupy even more of Britain’s forces.

In the Caribbean, he did succeed in recapturing one small, former French fortification, but it was on a tiny island that had no commercial and little strategic value and it was returned to British hands again shortly afterwards, so that part of the strategy had fallen well short.

As for the Irish part of the expedition, no one can ever be quite sure why that didn’t happen. If Villeneuve had taken the most likely course for Ireland, he wouldn’t have come within a thousand miles of Calder’s force.

The most likely explanation would seem to be that Villeneuve was attempting to take a less obvious course, for fear that Nelson could outsail him if he took a more direct and expected route.

But why should he think that? Did he suspect that spies might have tipped off the British as to his ultimate intentions? Neither question has ever been answered satisfactorily.

What we do know is that Villeneuve was well aware of how big a botch he’d made of the entire operation and that he sat in Cadiz licking his psychological wounds and feeling very sorry for himself.

He had never wanted this command and yet he was a fervent patriot, who felt great shame at having let down his country and his emperor and he knew that time was running out for him, personally and not just for Napoleon’s plan to invade England.

Villeneuve was also aware that his fleet was in poor a shape - he had the advantage of numbers, but that was it. His men were disheartened, weakened by various outbreaks of disease and the French and Spanish sailors and officers all distrusted each other’s fighting abilities.

On the French side, this suspicion was well-founded, for most of the Spanish ships were manned by soldiers, or by beggars press-ganged from the streets of Cadiz and barely a man among them had experience of firing a cannon from a rolling ship.

In August, 1805, Napoleon was growing desperate - he had two thousand ships and ninety thousand men assembled along the coast of France, ready to strike at the old enemy, but he needed to bring the Royal Navy into a confrontation and inflict as much damage as possible, regardless of the cost to his own ships.

"Come into the Channel," he wrote to his admirals in that month. "Bring our united fleet and England is ours. If you are only there for 24 hours, all will be over and six centuries of shame and insult will be avenged.

"His Majesty counts for nothing the loss of his ships, his message ended, provided they are lost with glory."

In that short missive we may have the answer to one of the biggest questions of the Napoleonic Wars - why Napoleon Bonaparte seemed intent in including Britain in his list of conquests, when he could have avoided it completely.

Had he been content to leave Britain and her Empire alone - a simple treaty, or entente, would probably have done it - and concentrated on mainland Europe, he would like as not have succeeded in all his ambitions, especially if he had avoided Russia as well, at least until he had the rest of Europe under his banner.

However, Napoleon was not just a great military commander, he was also a great military historian and knew by heart the details of just about every battle the French had fought against the English since the thirteenth century - almost all of which they had lost heavily.

This rankled with him and he was determined to show that here, at last, France had a man who could thrash the British and turn back the balance of power to the days when the Norman French had conquered those “puny isles”.

If he was ever going to prove his point, it had to be now and, finally, he realised that his biggest mistake had been to appoint Villeneuve to command his Mediterranean Fleet.

Now, belatedly, he summoned the exceptionally capable Admiral Rosily and issued him with orders to assume command at Cadiz, despatching a messenger ahead, with orders for Villeneuve to return to France.

Villeneuve, however, still had his friends and supporters at court and it is believed that they sent a messenger, just hours ahead of Napoleon’s official courier, to warn the admiral of his impending dismissal.

Admiral Pierre-Charles Villeneuve knew only too well what his dismissal would mean - at the very least, a lifetime of disgrace, at worse, an appointment with Madame Guillotine. He made a decision and issued orders to put to sea, just hours before Napoleon’s orders arrived in Cadiz.

There is little doubt that his commanders gave the orders to weigh anchor with a feeling of impending doom in their hearts ...

On 20 October the Franco-Spanish fleet was spotted by a patrolling British frigate and flags broke out, from masthead to masthead, relaying the message:

"The French and Spanish are out at last. They outnumber us in ships and guns and men: we are on the eve of the greatest sea fight in history."

On board HMS Victory, Admiral Lord Nelson received this news with utmost calmness; here, at last, was his chance to smash the enemy completely and he had every confidence in his ships, his commanders, his men and, above all, his battle plan.

There was one thing you could say about Nelson - he never believed in playing for a draw and now, on the eve of Trafalgar, he knew, possibly better than anyone else, that nothing short of a decisive victory would do.

And, as he sat contemplatively in his cabin, aboard Victory on the eve of battle, he was only too aware that the fate of his country rested fairly and squarely in his own hands ...