http://forums.jag-lovers.org/avsn.php?1127284j74"Inner and outer rockers are major issues on MK2s, and many times you will get a rust hole in the middle of a door or, additionally in an S/420, in the middle of the rear fenders. Jaguar used sound-deadening pads in the middle of those large metal panels to cut down on drumming noises.
Unfortunately, those pads were made out of felt or jute. When the water
dripped down inside the doors, whether or not the bottom drains mentions by Clark are clear or not, the pads get wet. Wet equals rust, again from the inside out. I had a very nice Calif. black plate late S -type (all-syncro, late brakes) that did not have any lower fender rust popping through its still original paint. But, there was a hole in the middle of one of the fenders from the wet anti-drum pad. Obviously this otherwise pretty dry car had gotten water on the pad, so, it is just a matter of time before the lower fender rust will begin showing."