Brake servo failure

[Raistlin]

One of the main bugbears for the diesel engined variant of the S-Type is brake servo failure characterised by normal braking in the short term but a sudden and scary hard pedal in long term braking due to the total exhaustion of vacuum caused by a leak in the servo's diaphragm / seals.

Why am I mentioning this in the XF section?

Well, it became apparent today that the later, 3.0L diesel variants of the XF use the same servo as the diesel engined S-Types, albeit a different part number and I was wondering if there was any developing history of this fault in the XF range of cars, or whether the problem, said to be caused by leakage from the master cylinder, has been recognised by Jaguar and rectified.

Any input would be most welcome and most useful of course, because if the problem HAS been fixed then there is a way for S-Type diesel owners to avoid this sort of thing.

Thank you