Vcolborn

I need some insight. I drove then parked my XJ8, which has 101,000 miles on it. It ran great, as usual. The next day it would not start. I took to the mechanic. They said that on one bank of cylinders there is no compression. I know little about the engines but it sounds strange to me. I mean, is there a possibility of a single point of failure on compression, especially one that would only affect one side of the engine? I hope that someone on here can give me a little guidance as to what the problem could be. Thank