Perhaps the “magic” of that dragon’s defense would be tied to the ritual of knighting. The knight in question would have to have actually DONE something to earn the knighthood as opposed to merely being knighted in anticipation of worthy service. This would be a plot point.
So, the newest RAF fighter pilots wouldn’t be able to do a damn thing on their own, but Sir Bob Geldof could organize “DragonAid”, creating a massive concert that was a bardic ritual to aid the country in its anti-dragon campaign.
(At the peak, maybe he performs a duet of “Avalon” with Brian Ferry to rouse the spirit of King Arthur & his crew. Possibly other knightly spirits as well.)