It really was a blunder, a first-class professional error - not least because some of the letters were opened by the managers' secretaries. Not surprisingly, the managers were outraged.
What happened was that my administrator had prepared a letter to confirm the salary increases recommended by the directors. Just as I was rushing off to an important appointment, she stopped me in the corridor and said: 'The letters are ready. Is it all right to send them out?'
As I had previously checked the figures and knew they were correct, I replied: 'Yes, go ahead.' But I failed to check that she understood they were to be sent to the directors for passing on to their managers face to face.
As the personnel director who dealt with the senior management team, I ought to have ensured that the directors had the opportunity to tell their managers personally about the pay review. Directors and managers alike were understandably upset.
As soon as I discovered the blunder, I sent a note of apology to every director and manager, accepting full responsibility. I stressed that there was no question of the personnel department reneging on line management relationships. I also made a point of being very visible during the ensuing few days. My immediate apology had a positive effect, though I suppose the fact that the letters bore good news helped.
I am pleased to say none of my colleagues berated me.
To be forgiven for a blunder, you do need to have the basic goodwill of your colleagues. Fortunately, it happened when I was fairly well-established at the Stock Exchange. Quite a number of my colleagues seemed quite pleased that I had shown myself capable of making a mistake - and a big one at that.
So let me say this on the subject of mistakes. In business, you are often set up in a role where you can forget that you are human and fallible.
We all make mistakes and shouldn't be fearful about them. But you must act quickly to put them right. And don't ever pretend they haven't happened or seek to blame someone else.
What's more, people should not be punished for their mistakes. Unless, of course, they arise out of negligence. 'Empowerment' is a word much used these days. I call it a 'can-do attitude'.
If you punish people for their mistakes, they won't be creative and you lose more than you gain.
Lessons learned? My biggest mistake enabled me to reaffirm the importance of line management and staff relationships, and that at no time should personnel departments cut across that. It also brought home to me the importance of administrative staff being given clear procedures to work to if mistakes are to be avoided.
Communication on salary matters is just about the worst thing to get wrong. It's an area where great care has to be taken that the channels of communication are right.
Rhiannon Chapman, 46, is the director of The Industrial Society, the self-financing body dedicated to promoting productive relations at work. The society, which she joined in 1991 after 10 years as personnel director at the Stock Exchange, is the UK's largest independent provider of training and industrial services. Last year she turned its 1991 deficit of pounds 544,406 into a surplus of pounds 903,011 on a reduced income of pounds 15m. Ms Chapman, who is an independent governor of London Guildhall University (previously City Polytechnic), has spent 24 years in personnel and training roles.