Emmanuel, that is an interesting photo' as it shews the later single piece Inner Drive Shaft. I wonder if that is original or has it been uprated at some time ? In any event you will likely get your replacement nut here:
Pete Yale, Sales Co-ordinator
Tel : + 44 (0)1212492549
Fax : + 44 (0)1212492119
Mob : +44 (0)7753845661
e-mail: pete.yale@dana.com
Dana Light Axle Products Group
Birch Road, Witton, Birmingham, B6 7JR, United Kingdom
Failing that BPA Engineering are very good, see my previous post at
http://www.acownersclub.co.uk/forum/topic.asp?TOPIC_ID=2756 Either way you are in the fortunate position of having a set up that can make use of the later, stronger, components and it may be that you can find the nut easily, nearer home, via a Jaguar spares supplier.