@Reiver 2: "It's an Irish 'rebel' song, about an IRA contingent who tricked Dr. Johnson (not a rebel sympathizer) and commandeered his car to provide themselves with transportation to their assembly point at Dunbar."

@McGrath of Harlow: "My father used to say that Dr Johnson was in on it anyway, but he had to say the car was hijacked to keep out of trouble."

Back in the 1970s, I sang this song during a concert. Afterward, an old fellow (I guessed he was about 80 years old) came up to me, and he said, "You know that line in the song where it says 'Johnston he did grin'? Well, it's true. Johnston was a rebel sympathizer, but he had to pretend to support the British, so that he could have a permit to go around and visit his patients." He said, "And do you know how I know that? He was MY doctor!"