Martin,

"Green Linnet" isn't a real bird, it was originally an Irish code-name for Napoleon. Kind of similar to the code-name "Moor-Hen" that the Scots gave Bonnie Prince Charlie during the Jacobite rebellion.

At one time there was a (wishful and probably ill-founded) belief among some revolutionary-minded Irish, that if Nappy conquered England his first act would be to liberate Ireland.

Folks who held this belief were quietly hoping he'd win the war, and made preparations for his coming. But it's probably best they never found out firsthand the actual consequences of a French victory.