Question: By what year was the British Army playing a central role in the final defeat of Napoleon at Waterloo?
About the article "Napoleonic Wars", section "War between Britain and France, 1803–1814".

Candidate passages:
The famous defeat of the real life Napoleon took place in a region called Waterloo which is in Belgium.
Also, the army that bested him there was British.
The real life Napoleon also invaded Russia.
But contrary to the cartoon, he won that battle. 
Napoleon at Saint Helena (German: Napoleon auf Sankt Helena) is a 1929 German silent historical film directed by Lupu Pick and starring Werner Krauss, Hanna Ralph and Albert Bassermann.
The film depicts the final years of Napoleon between 1815 and 1821 during his period of exile on the British Atlantic island of Saint Helena following his defeat at Waterloo. 
  In recognition of Napoleon's defeat, "to meet one's Waterloo" (or similar) has entered the English language as a phrase signifying a great test with a final and decisive outcome - generally one resulting in failure and proving vincibility for something or someone who had seemed unbeatable.
The Waterloo Medal was issued to all ranks of the British Army who participated, including supposedly a baby born on the field to one unit's auxiliary woman aide.
It was one of the first general medals issued.
One can be seen with Wellington's uniform in the basement at Apsley House.
When French President Jacques Chirac visited the UK to celebrate the centennial of the Entente Cordiale, the Waterloo Room in Windsor Castle was renamed the Music Room, and then renamed the Waterloo Room following Chirac's departure.
The famous quote attributed to Wellington "The battle of Waterloo was won on the playing fields of Eton" was probably apocryphal.
Unlike his older brother, Wellington was not an academic success at Eton; on one of his rare visits back there, the only athletic activities he could remember were skipping across a brook, and fisticuffs with a fellow student.
See also .
Jim DeMint, a Republican United States Senator of South Carolina, made a well-publicized comment during a conference call with conservative activists on July 17, 2009 in which he encouraged conservatives to go after President Barack Obama's Health Care Reform efforts, saying "we're able to stop Obama on this, it will be his Waterloo.
It will break him."
In response, DeMint's Facebook fan page was spammed with hundreds of postings of the link to the YouTube video of Abba's Waterloo.
After the passage of the health care reform bill, conservative pundit David Frum criticized the opposition strategy exemplified by DeMint's comment, saying, "it’s Waterloo all right: ours."
Some liberal commentators claimed that it was his Waterloo, as DeMint predicted, but that Obama played the role of Wellington rather than Napoleon.  
Waterloo may refer to:  Battle of Waterloo, a battle fought in 1815 near Waterloo, Belgium, in which Napoleon I met his final defeat  Anyone's final defeat can be idiomatically called their "Waterloo"  
The Battle of Ligny (16 June 1815) was the last victory of the military career of Napoleon I.
In this battle, French troops of the Armée du Nord under Napoleon's command, defeated a Prussian army under Field Marshal Blücher, near Ligny in present-day Belgium.
The bulk of the Prussian army survived, however, and went on to play a pivotal role two days later at the Battle of Waterloo.
In contrast to Blücher's forces, the left wing of Napoleon's army did not join the decisive engagement.
The battle of Ligny is a prime example of a tactical win and a strategic loss.
However, had the left wing of Napoleon's army succeeded in keeping the Prussian army from joining the British Army under Wellington at Waterloo, as the Emperor had planned, Napoleon might have won the Waterloo Campaign.