The Duke of Wellington once said that a man might as well write the story of a dance as write the story of a battle because too much is happening at once, but here's one man worth listening to.

He's called John Dickson and he was a weaver from Paisley who was in the middle of the blood and the death at Waterloo exactly 200 years ago. He looked into the face of the Little Corporal, Napoleon himself. He was there when the Scots Greys charged and cried: "Scotland for ever!" And he was right at the heart of one of the most significant and controversial moments of the battle.

But John Dickson's story comes with a warning, delivered two centuries after the battle by Dr Stuart Allan, a historian based at the National Museums of Scotland. As he shows me round the military collection at Edinburgh Castle, Allan points out some of the items connected with Dickson but asks me to remember that there are no certainties in his story. "The certainties that people look for in the past, about glory or unity - or the opposite - do not exist," he says. "It's never as simple as that."

Allan is taking me round the collection at the castle mainly to look at two items directly connected with Dickson ahead of the 200th anniversary of Waterloo next week. The first item is his sword, which the 26-year-old Scotsman used to slash and hack at the enemy in the middle of a crowd of 200,000 men packed into two square miles. "I can hear the Frenchmen yet," he once wrote, "crying when I struck at them and the long-drawn hiss through their teeth as my sword went home."

And here's a picture of Dickson himself - a portrait painted when he was an old man and liked to tell his stories of Waterloo at a pub in Crail on the Fife coast. On the anniversary itself, the whole village would turn out to do honour to him and a crowd would gather to hear his stories of joining the Scottish cavalry regiment the 2nd North British Dragoons - otherwise known as the Royal Scots Greys.

Today, Allan and I are going through Dickson's story again, partly to explore what it was like to be an ordinary soldier during the Napoleonic Wars, but also to explore some of the lessons of Waterloo as well as some of the striking similarities between then and now. Waterloo was 200 years ago, but it is not a distant battle.

We start at the beginning of Dickson's story, which is included in a BBC Scotland documentary The Scots at Waterloo. Dickson was born in April 1789 and joined the army when he was 17, for much the same reason that many teenagers join up now. Dickson had been working as a weaver but the industry in Scotland was in a perilous state thanks to the war with the French and so he joined the army as a private. Then, as now, there would have been a large contingent in the British army of men from poorer backgrounds who saw security in the military; it was a way out economically.

By the time of Waterloo, Dickson had been in the army for nine years and was an experienced cavalryman in the Greys, so named because of their famous grey horses. In his old age, on one of those nights in the pub, he recalled the eve of the battle and how he and his comrades waited for action. They sat around a campfire and could hear a loud, rumbling noise about a mile away which they knew to be the French artillery and wagons coming up. "About 11 o'clock that night, a fearful storm burst over us," he said. "It was a battle royal of the elements, as if the whole clouds were going to fall on us. We said it was a warning to Bonaparte that all nature was angry at him."

On the morning of the battle itself, their blood was up and Dickson was in an excitable mood, which helps explain what happened next. The armies of Britain and Prussia were railed against the 124,000 followers of Napoleon and the Allies were not expected to win the day. Napoleon himself was so convinced that he could beat Wellington that on the morning of the battle he told his staff that they would be dining in Brussels by evening. But then the Allies turned and faced the French at Waterloo.

Dickson recalls being ordered to charge the massive French infantry. "It was a grand sight to see the long line of giant grey horses dashing along with flowing manes and heads down," he said. "All of us were greatly excited and began crying: 'Scotland for ever.'"

The charge of the Scots Greys has since become one of the most famous incidents of Waterloo, mainly because during it, one of their number, Sergeant Charles Ewart, seized the French eagle of the 45th Regiment du Ligne, known as the Invincibles. Many years later, when the Victorians were romanticising and idealising Waterloo, the incident was portrayed in a painting by Richard Ansdell called The Fight for the Standard, which now hangs in the Great Hall of Edinburgh Castle. The eagle itself is also kept at the castle, although it is currently at the National Museums as the centrepiece of its Waterloo exhibition.

Allan explains that the eagles were not of any practical use, but had great symbolic importance so the capture of one by the Scots Greys was of huge significance. "The eagles were conferred by Napoleon himself with the injunction that they had to be defended with their lives so the capture of standards is a big deal," says Allan.

"It wasn't the first time, but two were captured at Waterloo and sent back with Wellington's despatch as evidence of the victory. They were taken to the Prince Regent and laid at his feet by an officer who still had his battlefield uniform on. The eagles embodied the honour of the regiment - the eagle was Napoleon as emperor, it was his symbol and it had all the symbolism of ancient Rome. It was an injunction for regiments to stand their ground. And once captured, they were used as propaganda weapons."

Dickson also talked about being beside Ewart when he captured the eagle and his words, although almost certainly exaggerated, do something to summon up the real horror of a Napoleonic battle. Paintings such as The Fight for the Standard make battle look almost elegant and bloodless but the reality was the opposite: violent and ugly, a sea of men slashing and hacking at each other, many killed instantly, many losing limbs and dying more slowly.

Dickson describes how he charged up to six Frenchmen who were trying to escape with the standard. "Ewart had finished two of them," he says, "and was in the act of striking a third man, who held the eagle; the next moment I saw Ewart cut him down and he fell dead. I was just in time to thwart a bayonet thrust that was aimed at the sergeant's neck. Almost single handed, Ewart had captured the Imperial Eagle of the Invincibles."

But what about the bigger picture? What did the charge of the Scots Greys achieve? Was it a victory or a disaster? "It was a bit of both," says Allan. "This is a French infantry assault that is already being turned back and then they send in the cavalry. So the Union Brigade charges and does serious damage to the infantry and the eagles are captured, but it's in the nature of these things that once it's started it's quite hard to stop so they went too far and, if you read Dickson's account, a lot of the really heavy hand-to-hand fighting is in the latter part of the charge, in among the French guns, and they got very cut up and lost most of the force. Sending the cavalry in is a bit of a blunt instrument - it's your heaviest force to strike a blow, but there's not a lot of subtlety in it."

In fact, the Scots Greys lost most of their force and there were scarcely 50 of the 400-strong regiment still alive after the charge (Dickson himself was unscathed). And yet, because of Ewart's bravery and the symbolism of the eagle, the charge came to be seen as one of the pivotal moments of Waterloo - a view that Allan has little patience for. "There was certainly a feeling at the time, and closely afterwards, among non-Scots that the Scots seemed to be getting all the attention," he says. So it wasn't the Scots wot won it? "No," he says.

In the years after the battle, Dickson kept telling his stories (including spotting Napoleon himself and allegedly hearing him say: "These terrible Greys - how they fight!") and the legend of the battle grew and grew, even though it wasn't even the biggest or most important of the battles of the Napoleonic Wars. In the process, some of the more subtle aspects of the battle and its aftermath were lost and Dr Allan is keen to see them revived. It took time, for example, for the legend of Wellington to grow, despite his obvious achievements on the battlefield.

"As a soldier, I have a very positive view of Wellington and very few people would argue with that," says Allan. "At Waterloo he did what he had to do - he'd chosen where he was going to fight and he stopped Napoleon and I don't think people could ask much more of him.

"But he was also quite controversial as a political figure, identifying with the government. Even before his fame, his family was closely identified with the Tories so he becomes that again and it's not until quite late in his life that people see past his partisan view and he again becomes a figure remembered for Waterloo. The statues of him in Glasgow and Edinburgh are much later, towards the end of his life."

Allan also says there was a surprising level of debate and division about the battle and the greater war - just as there is about modern wars. "You'd be surprised," he says. "I have been reading quite a lot of contemporary newspapers and it becomes apparent quite quickly that it was not that dissimilar from now - no-one is going to criticise the troops because that would be bad form. But if you were a supporter of the government - if you were a Tory - then Waterloo was the greatest achievement in British history and it's all about patriotism. If you're a Whig, though, then the war could have been avoided, it was not being organised properly, and people were making money out of the war."

What is also sometimes forgotten is that Waterloo and its aftermath led to considerable social unrest, not least in Scotland where the Red Clydesiders flexed their muscles not for the first or last time. The Victorian ideal, and the popular image, is of the glorious British against the French, but there were many people in this country who supported the ideals of the French Revolution and saw Napoleon as its saviour.

"Radicalism had gone quiet since the 1790s," says Allan, "but after the war, you've got people out of work, people on very low wages and unhappiness that grievances are not being addressed by a government that has no real democratic aspect to it at all and that breaks out in different ways in different parts of the country. In Scotland, it breaks out in the industrial west because that's where you have people suffering most. But the big public demonstrations didn't produce any result. It went off at half-cock."

As for Dickson, after the battle he returned home and was promoted to sergeant, before being discharged in 1834. He then moved to Crail and raised a family. Crail woman Jean Durie has researched Dickson and believes more should be known about his life and work. "If it hadn't been for Dickson, we wouldn't know as much as we do about Waterloo," she says.

Durie first became interested in Dickson through a family connection - her grandparents were friends with Dickson's two grandchildren and executors of their will. "I first heard about John through the family and I got landed with the bits that no-one else wanted, including some papers and documents," says Durie. "When I read his account, I got goosebumps because it's his own personal account; it's a super read, and I wanted to tell his story." Durie has now curated a small exhibition about Dickson at Crail Museum, which will run for the rest of the year.

On a much bigger scale, the National Museums of Scotland has mounted an exhibition that seeks to explain the iconic status of Waterloo, which Allan believes has endured in the popular imagination because of Napoleon.

"He was the most famous man in the world, he was an ogre figure in Britain for 15 years, but people were fascinated by him and it's the tragedy of Napoleon, the rise and fall, and rise and fall. It was about the final defeat of Napoleon and the fact it was a British general who delivered that final blow. It was an affirmation of Britain's world power which was now unchallenged so it's about that just as much as the actual battle itself.

"It's the end for Napoleon and that's why we remember it. But it's also the moment when Britain takes its place in the sun."

Waterloo - After the Battle is at the National Museums of Scotland in Edinburgh until September 27. Visit The John Dickson exhibition is at Crail Museum and Heritage Centre, Anstruther, Fife, for the rest of the year. Visit Lyon and Turnbull in Scotland is holding a sale of Waterloo memorabilia and artefacts on June 18. Visit