The following sequence of events may have a familiar ring. A terrorist attack takes place in central London. Six people are killed and some forty injured. The Prime Minister, having already banned all political demonstrations in London, now proposes the repeal of habeas corpus. The Metropolitan Police Commissioner gives an interview in the media in which he declares that there are 10,000 armed terrorists at large in London. An extra 50,000 special constables are sworn in to save the city. Teams of police oversee special workers, scouring the sewers for terrorist explosives. The Queen herself intervenes, observing that she was beginning to wish that all these terrorists would ‘be lynch-lawed on the spot’. A leading public intellectual observes that ‘[t]he London masses, who have shown great sympathy towards [the terrorists' cause] will be made wild and driven into the arms of a reactionary government’ as a result of the attack. But much later the atrocity is credited with having turned the thoughts of a future prime minister towards dealing not just with the terrorism but with its political causes as well.

These events are true, but drawn not from this century, not even from the last, but rather from 1867. The prime minister is Benjamin Disraeli not Tony Blair; the metropolitan police commissioner Richard Mayne rather than Sir Ian Blair or Sir John Stevens; the Queen is Victoria not Elizabeth the Second; the public intellectual is Karl Marx not Noam Chomsky; and the future PM is of course Gladstone rather than Gordon Brown (or David Cameron).