Might be worth separating the song from the tune in terms of where it first appears.

The tune "Over the Hills & Far Away" was very popular and was used for a number of 17th and early 18th century ballads.

The origins and dating of the song is another matter. The "Twa Recruiting Sergeants" mentions Gibralter, France and Spain which suggests it refers to the Wars of the Spanish Succession (1701-14) as Gibralter was captured by the British in 1713. However as it refers to these it could well have been composed after that war rather than during it.

Although an important Naval base Gibralter was not used as a military base by the British army in Spain during the Napoleonic Wars - the army was supplied through Portugal and the Northern Spanish ports which were closer.

As for George - there were four of them so you can take your pick, and that is before Mr Tams "tweaked" the words to make it fit as a theme for a series set in the Napoleonic Wars.