Don't tell RogerSomewhat left field, but after listening to Easy Star All-Stars, Dub Side OF The Moon, several times, I came away feeling that was the original and Pink Floyd were the copyists!
Here is one more that has been debated quite a bit
Original
Cover
I like the hopelessness of the 2nd version. Very sad and depressing but seems to impart the sentiment of the song in a way that seems appropreiate for the material