I've lost my oil cap!

after completing my work on the rear diff I took the defender for a quick run this morning and all seems fine, no funny noises or unusual rattles etc.. However this evening I opened the bonnet to make a start on the service and noticed the oil cap is missing.
There was not loads of oil everywhere just a small amount on the top of the rocker. When I changed the air filter there was some in the main pipe to the filter but none in the actual filter.

Last time I remember seeing the cap was when I cleaned it before I did any of the work I did however notice it seemed to be fairly loose fitting.

So has it just popped off or is this a engine out and throw the whole thing away type of job?!! These tend to be the only options on defenders!!

I had a quick search and by the looks of it as well as getting a new cap I'm going to replace the breather as well just in case that is causing a blockage, any other suggestions?

You could just buy a new oil cap, or am I missing something?

Well that's what I was going to do just seemed odd it went missing.

At least now I have the part number 710 thanks dippy!!

Easy mistake to make load of people have done it.

just ordered a new one along with a new breather, going to have a dig around the garage tonight for a temp one, anyone know if a B or A series cap would fit( MGB/MINI etc...) just trying to figure out what I might have at home