Many readers of Don DeLillo’s JFK assassination novel Libra criticised the story as ‘far-fetched’. DeLillo’s novelistic thesis was that of ‘overshoot’, in the strategic sense of ‘exceeding requirements’. A phony “murder attempt” is planned by far-right military figures; a false trail, implicating Fidel Castro, is laid. The intention is to swing the shaken JFK towards a second, and hopefully successful, invasion of Cuba. The plotters, recruiting from Miami’s rabid Cuban exile community, have to choose gunmen who (a) are motivated to ‘hit’ Kennedy, but (b) will aim to miss. By the time anyone spots the rather obvious flaw in this plan, Jackie’s dress has already been ruined.

Libra may be fiction, but DeLillo knew whereof he wrote. Real overshoots are not hard to find; indeed, they’re something of an occupational hazard in covert work, as the vicious circle of secrecy and conspiracy constantly threatens to spiral out of control. Oliver North’s Contras, to take a good example, were initially instructed to ‘squeeze’ the government of Nicaragua. No one (to take the most generous view) foresaw that the ‘squeeze’ would be prolonged into a headlock at gunpoint, or that it would be necessary to fund it by profit-skimming a second illegal operation (hostage-trading with Iran). Nor is overshoot a new phenomenon. Nor, lest we forget, a purely American one.

In 1887, with Britain in the grip of regular ‘dynamite outrages’ by Irish nationalist terror groups, British police revealed the existence of the ‘Jubilee Plot’, a plan to blow up Westminster Abbey during a service of Thanksgiving on Queen Victoria’s Golden Jubilee – with her, and half the British Cabinet, inside. This latter-day Gunpowder Plot, said the police, had been hatched by the Fenian secret society, the Clan na Gael, based in New York. The terrorist bombers were linked, by letters, to Charles Parnell and other Irish MPs who had been pressing the Commons for Home Rule. The ‘ringleader’ of the plot, General Francis Millen of the Clan na Gael, was offered the then-astronomical sum of £10,000 to return to Britain to testify, but was found dead before he could do so.

As history books have always told us, the case against the Parnellites fell apart when the letters were exposed as forgeries, cooked up by Dublin journalist Richard Pigott and sold to The Times (a dress rehearsal for the 1924 ‘Zinoviev Letter’ that destroyed the UK’s first Labour government).

What history books have not hitherto recorded, however, is that Millen had been recruited by the British government to stir the Fenians into bombing Britain – a passive-agressive scheme designed to rebound and discred it the Home Rule movement. Amid the genuine terrorist explosions that struck Britain as a result of this provocation, the Jubilee Plot was floated as a scare story with ‘leads’ (the Pigott forgeries) intended to smear the Parnellites out of political existence.

But Millen the agent provocateur had been a little too provocatif: unknown to his British masters, Millen’s enthusiasm had meant that the Jubilee Plot had become real. Two Irish-Americans carrying the dynamite for the job only missed their appointment with Her Majesty because a trans-Atlantic liner unexpectedly had no empty berths. They eventually arrived in Britain on the day of the service – but at Liverpool. At this point, the safety-curtain of state descended sharply on the half-farcical near-tragedy, and a proto-Warren Commission was appointed to stifle the evidence.

And the best thing about all this is that, unlike Libra, it’s not fiction. Working from government records that have been classified for 114 years, Campbell has untangled the hare-brained schemes and in-fighting of the embryonic British secret services (plus ça change!) with skill. The narrative, incidentally, spans the period of the Whitechapel murders: Ripper fans will find many familiar faces at work in the background of Fenian Fire, although Campbell does not deface his awesome work with attempts at Ripperology.

I have just one complaint about this book: it is damnably complicated. The multiple splintered Fenian groups are enough, as my late Irish aunt would say, to give yer arse a headache, and the way in which the narrative leaps back and forth in time can occasionally give you the sensation of having turned two pages at once. But the former is certainly unavoidable, and it’s difficult to see how the latter could have been circumvented without loss of detail. This is, simply, a timely and stunning book.