I've been leading a double life for 30 years. In that time I've been a teacher, but also written or edited 16 books on English literature or modern naval history. No one bothered much when it was academic books. All of a sudden, however, and without quite realising it, I seem to have changed the rules by writing fiction.
Writing the novel, book number 17, fulfils an ambition I've had for years. It's historical fiction, based on the Gunpowder Plot. For me, the interest is not in comparing writing fiction with writing academic books. It is comparing being a head with being a writer.
Headship is an extraordinarily public act. You are on show from the moment you arrive to the moment you leave. You are on show out of hours as well, known to hundreds and even thousands of children and their parents in your community.
Heads and teachers are owned by the job. They have to accept double standards, one pattern of behaviour for them and one pattern for most other professionals. No teacher could have thumped a heckler and hoped to retain their job as John Prescott did.
We are moral and behavioural role models in a way that applies to no other profession except judges and clergy.
There's no such thing as loneliness for a teacher or a head. Every aspect of your job relates to other people, either children or colleagues. You have to take decisions, but it's very rare to be able or want to take a decision without extensive consultation. No decision is truly personal. There's always advice to be had from others, always a higher authority in teaching, be it governors or the education authority.
At every stage there are procedures to be observed. There are also opportunities to check one's progress, from a formal inspection or an appraisal to the dread moment when the coughing in assembly proves that you have truly lost their attention. Teachers interact with their audience as intensively as an actor, but for far longer periods.
There's a lot of writing, of course. That letter to the parent may take half an hour or longer to compose, but the rules by which it is written are set for you, and the task once done is truly complete.
As a head you get respect as much for the post you hold as for the person you are. People can guard their tongues in the face of the person who will write their next reference for a job or university admission.
One recent, unpleasant development is the killing of creativity in teaching, except in a few privileged cases. It is increasingly about ticking a box instead of firing an imagination.
Compare that with writing. It is one of the most private acts. When you close the study door, there is just you, and the book.
The decisions you take as a writer are taken in the privacy of your own room, consulting with yourself. There's no advice, no procedures and only a cruel final appraisal, when the book either sells or bombs. There's no continual feedback. You'll learn your readers' response in six months, maybe a year. Half an hour does and dusts a letter to a parent. Three hours can produce three words as an author, with no guarantee that any more will ever flow.
There's also no automatic respect for a writer, although there are people aplenty who will ring you up and tell you that Chapter 3 is rubbish. There's no authority as an author, only the words.
Writing is the loneliness of the long-distance runner. It's utterly different from the way I spend most of my life. That's why it's the best holiday I know. It may sound odd, but it's the way I relax. That's why I find it easy.
Martin Stephen is High Master of The Manchester Grammar School. His first novel, "The Desperate Remedy: Henry Gresham and the Gunpowder Plot", is published by Little, Brown