Most people will never get this deep into their XJS. But I am a glutton for punishment. Anyway after looking at these earlier today it is almost certain that leaking here will have water running down between the inner and outer guard, eventually finding its way down to the radius arm mount.

Mine were broken and leaking for sure as I had a small amount of rust in the radius arm mount as well as rust in the wheel arch. This almost certainly came from the vent leaking as I my rear screen and quarter windows were water tight.

The silly flaps were very broken so I removed these and replaced them with aluminum. Then welded a new bit of plastic in the lower corner. These will then be fitted using sikoflex and rivets to prevent leaking in the future.