Written by Leslie Bricusse, the number got an Oscar nomination for Best Song. It's performed here by the wonderful, though little-known to American audiences, Anton Rodgers (who had a standout co-starring role as he charming con man Alfred Jingle in another Dickens-based British musical, my fave and oft-mentioned Pickwick), along with an assist here from Albert Finney.
The scene takes place during the Ghost of Christmas Yet to Come. No one is able to see Scrooge, therefore, and he's unaware that the people are not cheering him for being such a hearty good fellow, but rather the street food vendor Tom Jenkins who's thankful to Scrooge for something very different.