Let me get this right,...
your supervisor instructed you to make a change that cost you your job. How did this happen without lawyers / violence becoming involved?
Forget ITIL, agile or any other methodology, if someone invents a way of providing evidence capture on IT systems to a legally submittable level (before, after and authority to proceed), and a way of challenging technical decisions in a legal forum in a quick and relatively painless manner, 50% of British IT managers will resign in fright and all of a sudden projects will actually be delivered on time.
I had a manager who insisted that the operators only needed to see the 10 commonly occurring types of error AND NO OTHERS. I pointed out any new and interesting errors would go un-noticed until their impact was felt, and this was a risk to the business. "Tough, over-ruled!" came the response. And then 6 months later the systems catastrophically shut down due to overheating. When the main director comes knocking on my door asking why monitoring did not pick this up, I sent him the meeting minutes detailing the decision, a snapshot of the monitoring tool showing the SNMP alerts for the temperature warnings (not on the top 10, naturally) occurring for 2 hours before the event, and copied in a yahoo email address (that I created myself) called "whittleandcrouchassocs@[etc]". The issue seems to be dropped after that.
(Bonus points for those who can identify the TV program I got the lawyer names off.)