They may not be written down but everyone knows what they are even if they don’t know them as London Rules. Always, always cover your arse. In local government this can take the form of sending an email to your boss after the event, casually dropping it into your next one to one or speaking to a number of people in HR/Finance until you get the right response. Personally I always thought London Rules didn’t apply to me.
I operated below the radar. I always assumed something was permitted unless it was explicitly forbidden. I never asked permission. I did ask for advice as in “ how would you go about....” If called to account I had my reasoning clear and was ready to explain my thinking. Of course it was a risky but it got things done. Which meant some weeks I was the hero and some weeks I was the villain.