Don't know whether that's true or not (that the Duke of Wellington said that) but... One year later (1815), he handed the french's arses back to them big, big, big, times at Waterloo.
Basically the battle of Waterloo (a few kilometers away from where I was born) is considered the time when the UK overtook France as the world's number one superpower.
Since then both have only ever been falling in the rankings and it doesn't look like that fall is going to stop anytime soon but that's another topic.