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According to the service manual, axel nuts should not be reused.
When removing the axels for any reason, (replace wheel bearings or relubricate CV joints) the same logic applies.
As the replacement nut specification was not readily available, this post:

X-Type Axle Nut Dimensions: M22-1.5

Axle Nut Size (mm) M22

Axle Nut Thread Size (mm) 1.5

A 32mm size socket wrench is usually required but may vary.

The axle nut torque for a Jaguar X-Type from 2002–2008 is 200 ft-lbs or 270 Nm.

It's important to slowly tighten the axel nut to the final torque, loading the bearings and thus setting the geometry of the rolling elements.
If the torque isn't set correctly, the bearings may wear out prematurely.