There is an order to this: heads of smaller schools move on to bigger, high-achieving ones. We know where we are in this pecking order. It will be a shame to see the head go but it was inevitable.
So the machinery cranks into life. There is a procedure to follow, and I am now part of it. I have never aspired to headship with any conviction and it is now certainly not on my agenda. It is my job to ensure a smooth succession.
The first thing I do is tell the governors that I am not a candidate, but that I will be happy to manage the process. My agenda is no different from theirs. I want the best person. I might not be there to see what they do, but the school is important to me. It has been my working life for 15 years, and the people I have met are part of my memories. Now I have the opportunity to see a new dawn in the school and it is good to be part of that.
They can be confident that I have no axe to grind, no nest to feather. I am not there to cloud their judgements. I will make sure it all runs smoothly without being involved in any decision. Then I have to tell the staff. Even at this early stage in the process, staffroom politics has its part to play.
They need to know exactly what my plans are. I could not possibly wait until an appointment is made before I tell them that it is my intention to retire. If I did that, the staffroom would be awash with rumour about my refusal to work with the new appointment.
So I tell them. It is a big moment for me. Suddenly, and without any overall plan or strategy, a big decision has taken shape. Now there is no going back. It isn't what I had planned but the appointment of a new head changes many things and it would not be right for me to hang on for a few months more, like a millstone.
It is not a case of falling on my sword; suddenly it is the right time. I do not want to be a symbol of the past. A head appointment, we are just beginning to realise, is a central event, with an impact upon all aspects of the school's life. Everything changes.
The staff themselves do not recognise the significance of this moment for me. It is part of the temporary gossip in the classroom but is swiftly replaced by other more pressing issues, like break-time coffee.
The first step is to gather information about other schools. What do their adverts look like? I respond to a few and get their application packs - all very glossy and smart. We will have a lot to live up to.
There is not much difference in the nature of the material included. The application packs show how much responsibility the post carries and the different groups a head must come to represent. Whatever influence and salary the post might command, you can never pick and choose the bits you fancy. Everything is yours. No wonder there aren't that many applicants these days.
And when you see the responsibilities laid out like this, then we start to worry. Two local schools are also looking for heads. One is re-advertising for the second time, the other for the third. Is there really a field of genuine candidates out there? We shall see.
So a word of warning. If you are advertising for a head and you have a shed full of responses, don't call for the party hats. It might just be me trying to nick your ideas.
Geoff Brookes is deputy head of Cefn Hengoed comprehensive in Swansea