Dragon slayer sword

I feel that access to the kings strategist would be as (If not more) important than the all the smiths in the kingdom.
That being said, and wether or not a sword must be used to slay the beast, I'd use a spear, something along the lines of a lance or halberd to bread down and open up the scales, then use a DSA elite to make the killing blow. Thise things are HARD.

Hmmm, anyone mention reptiles are cold-blooded?

Of course, it depends on the dragon.

Is it one of those more or less cow-sized St. George type thingies, a gigantic thoroughly poisonous serpent like Fafnir, a "bloody great hot flying thing" (as sir Terry put it) like Vermithrax Pejorative or a Glorantha style slumbering elemental force often mistaken for a mountain range whose dreams are real enough that most mortals call them "dragons"?

But going with the Vermithrax-a-like specified in the OP, yeah, a heavy spear and a large shield would seem like the close combat weapons system of choice. A good strong bow would be even better, especially if I could round up the Black Arrow...

That... or just the Black Arrow. (THE Black Arrow, mind, not the once-mass-produced ballista bolts from the movie.)

“Arrow! Black arrow! I have saved you to the last. You have never failed me and I have always recovered you. I had you from my father and he from of old. If ever you came from the forges of the true king under the Mountain, go now and speed well!”