That day, I again saw Salafists outside the Tube station. This time they thrust a pamphlet into my hand. It was headed: “A warning against terror groups ISIS & al-Qaedah [sic] and the correct Islamic position regarding them!” My daughter chided me for my suspicions about our proselytising Islamists. The pamphlet came larded with quotations from the Koran and the Prophet Muhammad and his Companions, as well as Islamic scholars, past and present, including the Grand Mufti of Saudi Arabia (the same one who had just condemned chess as un-Islamic). It claimed that modern movements such as the Muslim Brotherhood, al-Qaeda and IS were all ideological descendants of the Kharijite sect, whom the Prophet himself had threatened to exterminate. The Salafists alone, it went on, had spoken out against these extremists.

This is, of course, propaganda. In reality, IS, al-Qaeda and the Muslim Brotherhood are Sunnis, not Kharijites. The premise of the polemic is false, like much else in this pamphlet. For example, it also claims that “severing the heads of the enemy in war is not a practice condoned by Islam and was not a practice of the Prophet or his companions”. Yet Muhammad’s first biographer, Ibn Ishaq, describes in detail how the Prophet himself personally beheaded between 600 and 900 Jewish prisoners of the Banu Qurayza tribe in 627. The denial of such facts is not only a problem for Islam.

Salafists — who dominate many of the mosques in London and elsewhere in Britain — differ from IS about means rather than ends. They wish to live under sharia law in Britain, they define jihad as “a just conventional war to prevent or repel oppression”, and their ultimate goal is the restoration of the caliphate — though they reject “the imposter caliph” Abu Bakr al-Baghdadi. The pamphlet indicated that this Salafist group had a mosque less than a mile from where I live, of which I was quite unaware. Are the authorities aware of it? They are struggling to keep pace with the number of mosques, which is rising just as rapidly as mainstream churches are closing.

Indeed, what has emerged before our eyes in Britain is a kind of Islamist state within a state. Alongside the Salafist movement, which originates in the Middle East, the Deobandi tradition, which predominates among Muslims of Pakistani, Bangladeshi and Kashmiri background, also has links to the Taliban. A new survey by ICM with the former head of the Equality and Human Rights Commission, Trevor Phillips, for Channel Four and the Sunday Times confirms that Salafists are fast becoming the dominant influence on British Islam. Nearly a quarter (23 per cent) of a sample of 1,081 adult Muslims want to see “areas of Britain in which sharia law is introduced instead of British law”. Nearly a third (31 per cent) of them think “it is acceptable for a British Muslim to keep more than one wife”, even though polygamy is in theory punishable by up to five years imprisonment. Wives should “always obey their husbands”, according to 39 per cent; the survey did not ask about the Koran’s injunction to husbands to “chastise” their wives, but Trevor Phillips sees it as “a clear invitation to legitimise domestic violence”. About 5 per cent of British Muslims sympathise with stoning adulterers. That may seem a small percentage, but only 66 per cent completely condemn such executions. This suggests that about a third would go along with such punishments under certain circumstances.