have a look at this parts diagram I have attached.

When stripping the girlfriends axle out there were two Retaining Plates (number 13) fitted..... per side... just doubled up along with a paper gasket.

Is there any reason why there may have been two? maybe an old garage trick to apply more pressure to the seal??

Any thoughts?

no reason that i know of, but when we used to build the non current new axles for lr (assembled from a kit of parts supplied by lr)110s used 2 per side 90s 1 , in all other aspects apart from calipers axles for 110 and 90 were identical, i used to write up the build lists then send them over to unipart who then looked over the list and signed it off when satisfied , one axle build had 4 chrome balls as the unipart engineer insisted it should have however much i tried to explain, the company i worked at just ended up with huge stocks of free chrome balls , i presume when he looked at parts diagram he concluded 2 per side not 2 per axle

i can't see it doing anything bar spreading the load, as if it was twice as thick...

My 93 90 only had one each side, mates 86 90 had two as did a spare axle he bought.
I think the 110 he is now working on is also two per side.

My 90 was like that when i was stripping mine down had two on each side but haynes bible said 1 on each side so when i rebuilt them i just used 1 on each side, never had a prob