This is a painting of George and the Dragon and the museum doesn’t know the artist, although it suggests that it was painted between 1401 and 1425 in northern Europe. That gold background, likely using gold leaf, was used to indicate heaven, so this is a sacred story and not a bit of Norfolk everyday weather.
Despite it showing claws and teeth, I’m not entirely sure that the dragon was perhaps as scary looking as it could have been, nor, I think it’s fair to say, is the artist exactly George Stubbs with that horse painting. But, it’s got that rather positive imagery of the brave St. George saving the princess from the nasty serpent, I can imagine this quite sizeable artwork being displayed in a medieval church.