But the success of the various Dan Brown spinoffs has convinced me that I should get back to it; moreover, the success of those efforts has given me the idea for my story. My blockbuster will be based on the theory that Moses was given only seven commandments on Mount Sinai, the other three being added later by the church. Hey look, if you think that's outlandish, consider that the originals were carved in stone by someone hidden in a burning bush. Where's the physics in that?

The theory behind my thesis is as follows. The number 10 does not appear in the Bible and is a creation of Arab mathematicians about a thousand years ago. The only number with any sacred significance was seven: seven days of creation, seven years of plenty, seven gifts of the Holy Ghost, seven deadly sins, seven pillars of wisdom, seven wonders of the world, seven players in a netball team.

So there would be only seven commandments. The church added the one about going to Mass on Sunday, otherwise where would they get the finance for all those magnificent cathedrals? Napoleon, you may remember, tried to legislate a 10-day week to tie in with the metric system, but the church knocked that on the head after they worked out that a collection every 10 days would be less profitable than one every seven days.

The other commandments not in the originals were the sixth about not committing adultery, the ninth about not coveting your neighbour's wife and the 10th about not coveting his cattle. The last-named was added so people would not think the church was obsessed with sex when they added the two commandments about how people should behave in their intimate life. And, of course, after Augustine, they were obsessed.

I am not innumerate and I realise that if I take out four of the present 10 commandments, there are only six left. That is where my central character will find a missing commandment. There will be no shortage of sources - the Dead Sea Scrolls, the Nag Hamadi codices, the Gospel of Judas, some long-lost Gnostic texts hidden in a triple-locked vault a kilometre under the Vatican - and it will give me an excuse to rail against the commercialisation of these treasures.

What I haven't yet decided is what the lost commandment will be. I am tossing up between something that enshrines the place of women in religious rite - ''Thou shalt not keep thy wife from the altar'', that kind of thing - or a reference to care for the environment. Both are, of course, trendy and will help to sell the book. Moreover, we happen to know that each was central to the ritual and practice of the ancient Druids of Britain and Ireland. I'm sure I could conjure up some source to support a theory that one of the lesser apostles went to Britain and was influenced by Druidism. Bartholomew maybe. Why else would there be a major hospital in London named after him?

Now, all I need are some villains. Obviously, I can't use Opus Dei or people would think I was copying Dan Brown. The CIA and the KGB and the Freemasons have been done to death already. If I used the NSW Labor Right, that would not be understood overseas. Maybe something associated with Silvio Berlusconi or your man from Texas who almost brought on a new financial meltdown. Perhaps I could use Rupert Murdoch or people smugglers or one of the Muslim groups who are blamed for everything.

I will tart the story up with references to all kinds of pseudo-research and plenty of plausible conspiracy theories. There will be sex about page 40 - memo to self: must have Augustine early in story - and someone will die a gruesome death by page 100. And when people will inevitably complain that I am being irreligious, it will be easy to say that this is a work of fiction and bears no relation to fact. But there will be enough verifiable fact to confuse people.

Anyway, that's what I think I'll do: ''The Rule of Seven. A Novel.''