How do i make Marcurio wear expert robe of destruction. he's wearing apprentice robes but refuses to wear what i hand him.

What can i do?

i've tried reverse pickpocketing, but that doesnt work

Some Followers just won't wear anything you give them except what they don't already have - like a helm.

but Marcurio will wear iron armour when i hand that to him

EDIT: Eh, nevermind.