Do you remember that ghastly election speech by Margaret Thatcher, months before the 2001 general election defeat that signalled the end of William Hague's leadership of the Conservative Party? At a party election rally in Plymouth, she stole the limelight from Hague.
"I was told beforehand my arrival was unscheduled," she said. "But on the way here I passed a local cinema and it turns out you were expecting me after all. The billboard read The Mummy Returns."
There is nothing more off-putting than a leader, chief executive or chair who cannot let go. It makes them look ridiculous and fatally undermines their successor.
That's the theory and it is, in general terms, universally accepted as the truth. The problem comes when applying 'on-paper' theories to the real world.
Our sector is littered with too many examples of former bosses who couldn't leave the new regime to get on with the job in hand. I suffered a few in my time. My immediate predecessor as chair of Aspire was a wonderful, avuncular man, with whom I am still (I hope) good friends.
Coming in as a new broom, I decided there were a few corners in the charity that needed a good sweep. This process involved dislodging some trustees appointed by my predecessor, and they inevitably turned to him with tales about how dictatorial I was being.
The correct response would have been for him to keep well out of it, something that he almost managed to do. However, he did telephone me to say - in the nicest possible way - that I had completely mishandled the whole episode. This might, indeed, have been true. One of my 'victims' had a habit of patronising me in such a way that it brought out the worst in me. Yet this doesn't alter the fact that the telephone call was overstepping the mark.
Initially, I was furious, although I soon realised that the poor man was bound to say what he said. These were his friends: if he'd thought they were useless, he would have got rid of them before his departure.
I learnt an important lesson that day. When my time to bid farewell came, I vowed that I wouldn't leave behind a trustee board past its sell-by date. One of my last acts as chairman was to slim the membership to an essential core on which my successor could then build something in his own image. Of course, he might tell you a different story, but my heart was in the right place.
One of my final gestures as chair was to reintroduce an old friend to the fundraising team, a remarkable man who had been a major donor many years before.
I was tempted to convince myself that, since he was my contact and my friend, I would have to stay involved, just to make sure all went well. One of the benefits of age, however, is that you get better at seeing through your own mixed motives, so I left him and the charity to it.
Several months later, I received an email from my friend regarding a particular problem, asking me for help in sorting it out.
As it happens, I like sorting things out and, if I'm honest, there was a part of me that wanted to hear that the charity still needed me - that part of me was like Margaret Thatcher as she noticed that film poster.
Instead, I told my friend to be blunt with the current chair of trustees and that my involvement would only muddy the situation.
I'm not trying to present myself as a saintly model of restraint here. Rather, I want to illustrate how easy it is for a former chair to be lured into being a backseat driver.
All our good intentions can so easily go out of the window when we foolishly judge a situation to be so important that it justifies breaking all our vows of non-interference.
In my Catholic childhood, I was constantly told that contemplating committing the sin was as bad as actually doing it. As a former chair, I am therefore a repentant sinner.
Peter Stanford is a writer and broadcaster, and was a charity chair for more than 20 years