Like many I can remember every single boss I have had throughout my 30-year career, I have had good bosses, bad bosses, and at least one great boss.

But the most memorable, the most impactful and the most beneficial was the boss who wins the title of the worst boss I ever had.

Even though I only worked for him for a year those memories are the most vivid. Not only in recalling what he said, but also how he made me feel, and even now I sense my stress levels rising and it's over 15 years since I worked for him.

Every meeting was an ordeal, you never knew how he was going to react, he could go from mildly irritated to ax-wielding homicidal manic in a nano-second and it didn't matter whether it was your fault or not.

The worst days though were those when he was being nice, not that there were many of them, but they were so out of character that they were even more stressful than when he was shouting and screaming. A lot of the stress he created was just from the anticipation of how he would react, or how nasty or condescending he would be.

In terms of impact, he actually made me not want to come to work.

He took all of the pleasure out of the job, when I woke in the morning I would hope that I would have a cold, or be feeling ill just so I could call in sick. He did such a great job of undermining my confidence that I began to doubt myself, which then had a negative impact on the quality of my work, which would them justify his attitude and belittling approach.

I remember when I finally quit, my notice period was the longest 4 weeks of my life. I was worried daily that the company I was joining would change their minds and I would need to stay. I also felt guilty about leaving my team to have to deal with him, I had been a shield for them, protecting them from his wrath but I just couldn't do it anymore.

He was eroding my confidence, my self-esteem, and feelings of self-worth and for my own well being, I just had to leave. When I finally left, even though I was relieved many of those feelings came with me, and it was fully 12 months before I could shake off the detrimental impact he had had on me. Believing that I was the real cause of his behavior and it was all my fault. He was a master manipulator and had so many different ways of undermining people.

Fortunately, my next boss was a good boss, and that allowed me to realize the truth of the previous situation and to finally overcome the trauma and regain my self-confidence.

That was the bad and the ugly of working for the worst boss I ever had.

The good was that it taught me so much about leadership, especially about bad leadership.

It taught me the depth of impact that toxic leaders have on their teams, and the stranglehold they can have over their confidence and self-esteem. How bad leaders can dramatically impact employee engagement and the quality and quantity of the work that gets done.

It taught me about the importance of consistency and predictability and how that makes it easier for teams to work with you, instead of creating doubts impacts productivity.

It taught me so many things not to do as a leader, things that don't really get covered in leadership training.

Obviously, at the time I hated every second of working for him, but now looking back now there were so many lessons, so many things I have benefited from and it definitely helped me improve as a leader.