I have spent the last two years writing the remarkable story of how northern Irishmen played a leading role in one of the most audacious military expeditions in British history.
The army commander was Major General Robert Ross, from Rostrevor in Co Down, who had fought valiantly at the head of a brigade under Wellington in Spain and southern France.
In the spring of 1814, the Peninsular War was won, Napoleon had abdicated and Britain was free to turn its attention to another enemy, the United States of America.
Its fourth president, James Madison, had rather rashly declared war on the world's greatest naval power, because Britain was interfering with America's trade with France. Now Britain was free to fight back.
Many Napoleonic War veterans, including Ross, who had been looking forward to going home, were suddenly despatched across the Atlantic.
Ross found himself commanding an army of 4,500 men, ordered to "give the Americans a good drubbing". And next in rank below Ross was another Irishman, Colonel Arthur Brooke.
Two years of research in Northern Ireland, Washington and Baltimore, and many hours scanning letters and diaries and other accounts in British and American libraries, provided me with dramatic evidence of this extraordinary episode.
I was able to see the burn marks left by the British on the walls of the White House. And the abundance of eyewitness material allowed me to feel close to Ross, Brooke and many other colourful figures on both sides of the conflict. In Belfast's Public Records Office, I scanned the anxious letters Ross wrote to his wife, Elizabeth, who had been desperately awaiting his return to Rostrevor in the spring of 1814 and was now severely depressed.
On August 20 that year, Ross landed his men in Maryland and led them trudging through the appalling August heat 50 miles inland to a village called Bladensburg just five miles from Washington.
There they met Madison's army, which had been frantically assembled from a scattering of militia units from the neighbouring states, together with a small core of regular troops.
Their patriotic enthusiasm did much to make up for their lack of training and many were confident of victory. Madison and his wife, Dolley, had ordered a lavish dinner to be prepared for the US high command and the cabinet once the British invaders were scattered. The battle that then took place was one of the most shameful in US history. Ross's army routed an American force one-and-a-half times stronger than his own.
Only one or two American units put up a fight, but they were facing grizzled veterans, who had seen years of action against Napoleon's French armies in Europe. By dusk on August 24, the road to Washington was wide open to Ross's forces.
The British burst into the presidential mansion, already nicknamed the "White House", and were delighted to find 40 places neatly laid, with meat roasting on spits and Madison's best wine on the sideboard in handsome cut-glass decanters.
Ross reported that the meal intended for the Americans was "voraciously devoured by John Bull" and a toast "to the success of his Majesty's arms ... was drunk in the best wines." A young naval officer nipped upstairs and swopped his bloodstained shirt for one of Madison's neatly ironed white tunics on the chest of drawers in his bedroom.
After the meal, while one of the soldiers wrapped up the silver cutlery in the fine damask tablecloth, Ross coolly ordered the chairs placed on the table and the whole building set alight.
For good measure, Ross also set fire to the War Department, the Treasury and the State Department, as well as the two houses of Congress. One of Ross's staff said he would never forget the "destructive majesty of the flames". His men were, he reported, "artists at their work" of torching the city.
It was the single most destructive act committed by either side in the almost-forgotten war of 1812. One feature of it all was the revulsion some of Ross's own staff felt at the burning of the shrines of American democracy.
But Ross was unrepentant and went on to lead an attack on another – and richer – US city: Baltimore. Confident of success, he wrote to Elizabeth, assuring her that the war with America would not last long and he would soon return, never to leave again. But before she received the letter, he was fatally wounded.
It now fell to Arthur Brooke to take command for the final advance on Baltimore.
I visited the sumptuous residence in Colebrook, Co Fermanagh, home of the Brooke family, which also provided Winston Churchill with his right-hand man in the Second World War, Field Marshal Lord Alan Brooke. It was Brooke's fate to lead the army that had triumphed in Washington to failure at Baltimore.
The outcome of the confrontation that followed was to leave Brooke and his army deeply disappointed and the Americans convinced that they had won a stunning victory that would one day inspire their national anthem – The Star-Spangled Banner.