Not so fast
First you have to get the RHT to actually write it down. I had a manager ask me to basically reorganise my team to favour one person (newest personal recruit, personal friend of the director). I told him it basically changed the job role of 3 people, and that I needed it in writing. At which point he would look at his watch, go "Oh dear, I need to be somewhere" and skip out. This was followed by all of my own improvement initiatives being blocked based on something-or-other. (Repeat for 6 months).
My end game was to divvy up work based on the lowest common denominator (the newest recruit) and write prescriptive job taskings for everyone (I was being accused of bias against new recruit, so had to show I was treating everyone the same). Half the team left, they got in a new team lead after 6 months, then the other half of the team left (including me). The manager and director got booted at the next reorg due to high staff turnover.
Lesson; management hold the reins on tasking and can make your life more uncomfortable that you can make theirs. They can also blame faults from their lack of support, on you, because they are in those circles and you don't. The only influence you can have is on metrics they are evaluated by that you don't control (staff turnover, morale etc).
I am not friends with anyone on facebook from that job. Pity, I was there 11 years but the last 2 I would rather forget.