Ayatollah Khomeini issued a fatwa to that effect, which was then given effect in the Islamic Republic of Iran, so in the Islamic Republic of Iran, it's flexible enough to allow for sex changes, and it encourages sex changes. But if you want to change your religion in Iran, you've got some serious problems. There are other problems. You're allowed to change sex, but if you want to be a homosexual, theoretically at least, you face the death penalty. Quite how often these penalties are carried out is a moot point, but it's there on the statute books.

The first thing to say is that the ordinary criminal law in this country, the Human Rights Act, the Children's Act, all of the laws of the country take precedence, but what I'm also saying is that within the context of a secular country, which Britain now kind of is, or at least a country which purports to be relatively equal between religions, there should be some scope for allowing faith communities to govern themselves - subject to it being consensual and subject to everyone's human rights being observed.

Whenever one writes a book one should have a notional reader in mind.

I think it's important to understand Shari'a to be rooted in history - what we know about the history and what we don't know about the history. So then, if people want to argue, at least they're arguing from the same point and we know what we know, and we know what we don't know.

In 1979, you had the revolution in Iran. You had the Hudood Ordinances in Pakistan, which are the laws that are notoriously used against women, which are theoretically used against thieves although they're never carried out - an actual amputation or an actual stoning. The blasphemy laws, again, never actually carried out, though they're there, heavy with menace on the statute books.

There were periods in Islamic history when things like apostasy and blasphemy were made punishable. So you know it kind of depends - there's no argument, quite apart from the question of the divine or otherwise nature of the Qur'an, that huge swathes of Islamic law are man-made. Clerics here - in maintaining their power, will often try to elide that and say "Well no, actually this isn't man-made at all. Stoning is part of the divine revelation." It isn't in the Qur'an but the way this has been done over the years is to take the Hadith.

I was a teenager when General Zia took power in the Pakistan; I was in my twenties when I went there during the late 1980s and I saw then not only the novel punishments that he was introducing - because they were novel, and this is again something that's very important to understand, it's only in the last thirty, forty years, since 1979 in fact, that these penalties have been revived anywhere in the world apart from Saudi Arabia.