Half shaft spacer???

I got my defender back together today and drove it, it's driving fine with no noises or vibrations,
After looking at busters how to (after doing finishing the job) when he changed the cv there was a metal spacer as well as the wire clip.
Mine definitely did not have a spacer fitted on the half shaft so I haven't refitted one.
Just seen James martins reply on another post saying they all have them?
I take it it's to stop the half shaft coming out of the diff?.
Now I'm worried,

Anyone one ever seen a defender without this spacer/collar fitted?
I'm not using the motor until I know what the crack is.

i havent ,but whereas i would fit one i dont think youll get any issues running the vehicle for a while

Yeah iv ordered a spacer.
I'm going to strip it and see if it'll fit.
All I can it does is keep the raised shoulder of the half shaft in the seal in the swivel ball?