I can activate developer mode no problem but my Engineer cant see the option to do. Do i need to give him specific access rights ?

I have updated the answer, please check.
Hope you are not using any third-party add-ons which restrict debug mode user-wise.

no 3rd party add ons or anything attached to Odoo. we use Odoo as it is, no extras, no nothing. do i need to give hi mspecific access rights. my other users dont need developer mode but he does. is it possible to enable this under his user account somewhow ?

Did you try the second method? setting from the URL

Does he need to do that on his browser ?
we are not both based in the same place

Yes, it has to be on his browser.

I have asked him to do this when he gets back to his laptop. This will apply to a replicated test system also, as this does not show on my login to the test site and i still have dev mode. It does show on my live DB though

He has access to settings but does not have th edeveloper tools showing at the base. I am not sure why thy are not showing. Is there a specific access right i need to enable so he can see these