Hi,

I associate that more with the Mike Waterson/Lisa Carthy version, rather than Mike's own version. But OK:

"Talk of heroes, woe for Nelson,
... Sing the praise of Alexander,"
... Here we only have one hero,
... I'll tell to you his name."

British culture includes a certain amount of hero worship, to the point where historical heroes have been adapted into British stories. Horatio Nelson was a British admiral who is credited with the victory at the battle of Trafalgar, though he actually lost his life there. Alexander III of Macedonia was the conqueror of the known world of his time. The singer, very uncharacteristically by British standards, doesn't deem these people heroes of importance.

"... Master craftsman, skilled engraver,
... Jack Frost is his name."

Jack frost is Winter personified, the force that draws winter wonder on your windows and builds icicle structure from your house.

"From the cold wastes of Siberia ...
Till the winter time is gone."

Winter is coldest with wind from the east, thus from Siberia.
      

"Flew the eagle into Moscow,
Sure in its defeat.
Ran the bear and sprang the winter, ...
To perish in the blizzards and the gale."

Napoleon Bonaparte, (The French Eagle), had his troops attack Russia (the Russian Bear). Eventually, the sheer size of the country meant his troops were still underway by the time they should have conquered a solid foothold in Moscow to spend the winter. Napoleon retreated, but his troops could not be saved so easily from the inclement winter weather.
   

The whole story is someone thinking about winter, and what they consider the strongest force in the fields at that time of the year. If I wrote them out at my myshas.net website, my version has an introduction of the singer slumbering in his bed. I feel that approach links the parts together better.

BFN
Mysha